diff --git a/README.md b/README.md
index 126e2dc..cc3a45b 100644
--- a/README.md
+++ b/README.md
@@ -11,28 +11,38 @@ motorDSM contains an example IOC that is built if ``configure/CONFIG_SITE.local`
 
 # Running an example IOC
 
-To run the example IOC, in the ``iocs/dsmIOC/iocBoot/iocDsm`` directory, run
+To run the example IOC, build the packages listed below, then:  
 
-    $ ../../bin/linux-x86_64/dsm st.cmd.md90
+1. Follow the steps in "Configuring the system for attached controllers" below.
+2. Set the "EPICS_CA_ADDR_LIST" environment variable to include the IP address of the server.
+If it's running on the same computer, you can use the loopback IP address.  
+`export EPICS_CA_ADDR_LIST='127.0.0.1`  
+3. In the ``iocs/dsmIOC/iocBoot/iocDsm`` directory, run  
+```
+$ ../../bin/linux-x86_64/dsm st.cmd.md90
+```
 
 for one attached MD-90 controller, or
+```
+$ ../../bin/linux-x86_64/dsm st.cmd.md90.multi
+```
+for eight attached MD-90 controllers. Edit this file to use more than one unit; simply comment out the ones you don't need.  
 
-    $ ../../bin/linux-x86_64/dsm st.cmd.md90.multi
+4. Test using the `caget` and `caput` arguments as described in the "Example usage" section below.
 
-for eight attached MD-90 controllers. 
+# Configuring the system for attached controllers
+-------------------------------------------------
 
-You will need to set the path(s) for the serial port(s) in ``st.cmd.md90`` (for a single unit) or ``st.cmd.md90.multi`` (for multiple units).
-You will also need to ensure they match the names used in ``motor.substitutions.md90`` (or ``motor.substitutions.md90.multi``).
-By default, ports are assumed to be at ``/dev/ttyUSB0``, ``/dev/ttyUSB1``, etc.
-You will also need to comment or uncomment lines depending on the number of drivers you have connected. For each driver, make sure you uncomment/call the following functions:
+The following steps must be used in either st.cmd.md90 (for a single unit) or in st.cmd.md90.multiple (for multiple units).
+st.cmd.md90.multiple includes 8 motors predefined on /dev/ttyUSB0 through /dev/ttyUSB7. Comment out all motors you don't need.  
 
-**1. Define a new serial port named "serial0"**  
+**1. Define a new serial port named "serial0" and set the location of the physical port**  
 `drvAsynSerialPortConfigure([serial name], [device location], 0, 0, 0)`  
 *e.g., `drvAsynSerialPortConfigure("serial0", "/dev/ttyUSB0", 0, 0, 0)`*  
 
 **2. Configure the port**  
-- Baud = 115200<br>
-- Bits = 8<br>
+- Baud = 115200
+- Bits = 8
 - Parity = none
 - Stop bits = 1
 - Input end of message: "\r"
@@ -64,7 +74,7 @@ asynOctetDisconnect('initConnection')
 where `[controller name]` is the name of the motor to assign. Convention is to use "MD90n", starting with n=0.
 
 **5. Intialize the IOC**  
-After calling `iocInit`, run the following lines for each motor. The example below uses `DSM:m0` but it should be run for each line described in motor.substitutions.md90 (or motor.substitutions.md90.multiple).
+After the call to `iocInit` (still in the st.cmd.md90[.multiple] file), issue the following commands for each motor. The example below uses `DSM:m0` but it should be run for each line described in motor.substitutions.md90 (or motor.substitutions.md90.multiple).
 ````
 dbpf("DSM:m0.RTRY", "0")	#sets retries to 0; this is automatic on the MD90
 dbpf("DSM:m0.TWV", "0.1")	#Tweak distance
@@ -72,6 +82,13 @@ dbpf("DSM:m0.VMAX", "1.0")	#Sets max velocity to 1 mm/s
 dbpf("DSM:m0.HVEL", "1.0")	#Sets max velocity to 1 mm/s
 ````
 
+**6. Update the substitutions file**  
+Save and close the st.cmd file you've been configuring, then open the motor substitutions file (motor.substitutions.md90[.multiple]).
+Ensure the values in the `pattern` block's `PORT` field match the names used in the std.cmd file.
+Note that, despite this field being called "Port", they use the names of the MD90 Controller object defined above (by default, MD900, MD901, etc.
+Do __not__ use the direct serial port names (by default, serial0, serial1, etc.).  
+
+
 # Compiling motorDSM
 
 ------------------------
@@ -185,4 +202,4 @@ Moving to a position target:
 
 Setting a velocity target:  
 `./caput DSM:m0.VELO 0.5		#Sets velocity target to 0.5 mm/s`  
-Note that velocity targets are appropriate only. They adjust the step rate of the motor, and are not guaranteed to be exact.
\ No newline at end of file
+(Note that velocity targets are appropriate only. They adjust the step rate of the motor and are not guaranteed to be exact.)
\ No newline at end of file