The server should always be visible in the game lobby, but if you don't see it there, check the filter settings. If even that doesn't help, follow this guide:
1. Start Steam
2. Click View ->Servers at the top.
3. At the top, click on Favorites.
4. Click on add server
5. Enter the IP+Query port, which can be found on the main control page of YOUR server
6. You put search servers ....
7. Add this address to your favorites
8. In the list of servers you click on the "refresh" button
9. Click on your server in the list and connect
10. The game will start and you will be connected to the server
After this action you will always see the server in your favorites and history
