Here is a guide on how to find your server on the in-game server browser lists.
Firstly, make sure your server is fully updated.
Secondly, make sure you have ticked: Filters > Show empty servers
There are 2 in-game server lists, Server Browser (licensed servers) and Custom Servers (unlicensed servers).
If you haven't applied for a license, then your server will appear in the Custom Servers tab.
If you want to apply for a license, then follow this link: http://master.joinsquad.com/serverlicense (you then put your license details within the License.cfg found in Configuration Files of your game panel)
If you have a license and have correctly inserted into your License.cfg but it is still isn't appearing in the Server Browser, then check your license status of your server using this link: https://www.battlemetrics.com/servers/squad
There you can search for your server and at the top left, you should see "Licensed Server: True, Licensed". If it says anything else then please open a support ticket.