So I made this map using Hammer and I want to upload it the Workshop. However, In order to do so, There are compatibility issues when I use p2map_publish. It says I need to have:

Maps built using the Portal 2 Authoring Tools must have certain map instances added to them in order to work correctly with Steam Workshop. To make your maps Workshop compliant, simply follow these steps:
1.Add a func_instance to your map and set the filename to: sdk_content/maps/instances/p2editor/global_pti_ents.vmf.
2.To trigger the end of the map and open the voting dialog menu, trigger the logic_relay named @relay_pti_level_end.
3.Finally, to suppress the automatic voice over commentary by Cave Johnson, set the $disable_pti_audio keyvalue to 1. This step is optional and only necessary if you have your own dialog or story to tell.

So I did 1 without a problem, but I'm having some issues with 2. When I go to the trigger_once I have set as the exit, there is no 'trigger' option on the via this input and when I type it myself it comes up red. What do I do? If I can't use a trigger_once, what other options do I have?
Please & Thank You

What I do for my maps is I go into the Workshop related files, copy the @relay_pti_level_end and place it somewhere not in an instance. (Anywhere in the map will do) and then add the trigger outputs for it.

That's just what I do and my maps turn out fine. I've never cared to much for linking triggers with instances, as it is I don't use an instance for the chamber signs, I use what's in the instace but not as an instance.

It totally worked!!! Thanks.

No problem! Glad I could help.

what I do is just give the global_pti_ents a name (pti_ents)

Then add a trigger_once,
OnStarttouch, pti_ents, and select the only input you can.
That works too.

I did not give the instance a name or collapse it, seems like a waste of effort to me, but if you type in "@relay_pti_level_end" correctly as an output, the name should turn blue. The output will still say it's not working, and maybe the blue won't even appear for you, but it should work properly in-game... Also, don't forget the "@", as it's vital to your success.