As part of your application you are required to submit your SteamURL which looks like http://steamcommunity.com/profiles/76561197998292312 or http://steamcommunity.com/id/Syncmaster667/.
Here is how you find yours:
1) First go to your steam profile:
2) Right click your avatar and select copy page url
3) Paste that steamURL into your application and continue with the application. Have fun applying and good luck!