Depending on which version you are running Survival Evolved or Primitive Plus will dictate where the server will show up.
If you have 111111111 in your total conversion mods section in Clanforge this will enable Primitive Plus, to find that you would first have to go to the right side of the main screen and select Primitive Plus Official.
When selected the game will briefly switch and you will have a new logo on screen showing Primitive Plus.

If you don't have this it will look like the standard below.

In the server browser you will find a number of different options and the server browser lists servers separately depending on password or no password. 

Key things to search for when attempting to find your server would be.
Name Filter: "Insert Part Name"

Show Password Protected: "Unticked" "Ticked" depending if you have this set or not. 

Session Filter: Unofficial PC Servers

You can search the entire server name or even just a section and it will list all servers with any part of what you are searching 

If you have set a password in Clanforge you would have to set Show Password Protected ticked as the browser separates Passworded and No Password into separate listing.

Error Joining Server

If you get an error while attempting to join the server please review the server name to ensure that it doesn't have / or \ included, due to SQL issues Clanforge converts these however ARK does not so it causes some issues.
Please replace them with anything like -