Here's a copy/paste from one of my posts. This should help:
"1) As N1GTL explained, you must first go to Radio Ergonomics > Display, and scroll down to “ID Display”. Use the dropdown next to the “PTT ID DISPLAY”, and select “Dispatch and Scan”.
2) Going back to the “Codeplug Configuration” tree, scroll down to “Conventional Configuration”, and select the “Conventional System” menu.
3) Right-click on the “Conventional System” menu, and select “Add”.
4) Now select the system that was just created, and left-click on it to open it.
5) Under “Conventional System Name”, erase the generic name and call it whatever you want. For this exercise, I’ve called mine “FIRE”.
6) Directly beneath that, locate the “System Type”. Mine is defaulted to “Astro”.
7) Use the dropdown to select “MDC”.
8) Now, go back to the “Codeplug Configuration” tree, and select “Conventional Personality”.
9) Assuming you already have created personalities, click on a personality that you want to assign the MDC system to. In this exercise, I’ve created “SGFD”. If you haven’t yet created a personality, go ahead and create one that will have this MDC system assigned to it.
10) Once you’ve built out the personality (an exercise I won’t go into here), continue scrolling down beyond the frequency inputs and options, and find the “Signaling” sub-menu.
11) Within the “Non-Astro” menu area, locate the “Signaling Type” dropdown menu, and select “MDC”.
12) Directly beneath that, locate the “System Number”. Change that to the system you created in step 5.
13) Going back to the “Codeplug Configuration” tree, scroll down to “Call List Configuration”, and click on “Unified Call List”.
14) Across the top of the screen are symbols. Click the “+” symbol to add a new “Contact Name”. This will create a generic contact; something along the lines of “Contact 00126”, in my case.
15) Highlight the generic contact name, and call it whatever you want. In my case, I’m going to call this contact “Battalion 1”.
16) After you’ve named your contact, click the little arrow to the left of the contact, so that the contact is highlighted blue.
17) Looking back up at your symbols across the top of the screen (where the “+” symbol is), select the blue folder (to the right of the trashcan). This opens additional options.
18) You now have several ID options, as well as the option to rename your contact if you so wish. Technically, you could have skipped step 4, and simply renamed the contact here. I learned that it’s easier to name it first, so that you are ensured that you have the correct contact open in this screen. Keeping the generic name, and renaming it from here, caused me confusion as I entered hundreds of these ID’s.
19) The option you want is “MDC Conventional ID”.
20) Along the “MDC” ribbon, click the “+” symbol.
21) Select the “System Name” from the dropdown menu. (Created in step 5, and assigned in step 12).
22) Under “Primary ID”, enter the MDC ID number
23) At this point, you are done. Your radio will read the ID and, if the ID has been created as per these steps, your screen will display the alias as opposed to the number.
The steps here are the same for Astro ID’s. The differences are:
1) When you build your system in steps 5, 6, and 7, you’ll select “Astro” as the signaling type.
2) When you build your conventional personality in steps 10, 11, and 12, you’ll instead use the “Astro” signaling sub-menu, and change the “Astro System” to whatever you created in steps 5, 6, and 7 (reference 1 above).
3) Then, instead of creating a “MDC” ID in step 19, you’ll create an “Astro Conventional ID” by selecting the Astro system you just created, and changing the “Individual ID” to whatever the correct number is.
