Please know that portal 2 has had an update... You used to be able to just open the publishing tool and click browse files. There is now extra steps involved, which is REALLY annoying. You will need to download the file from [Insert Link here] in order to continue.

Step 1: Download the file onto your computer and put it a folder somwhere easy to access.

Step 2: If you don't already have Winrar or 7zip... This is the time to get it as there is no other way to do this.

Step 3: Move the following 3 files from your portal 2/bin to a place where you will not lose them:
inputsystem.dll
localize.dll
steam_api.dll

Step 4: Extract the files from the folder of fix into your bin folder of portal 2

Step 5:Run p2publish and publish all your maps that you would like to publish.

Step 6: Once done publishing move the 3 files from your safekeeping folder back into portal 2/bin. When it asks you to replace the files click yes.

Step 7: Continue playing portal 2! Hope you enjoyed.