After you put in your top.gg link, you'll need to do the final step of setting up the Server Webhooks.
You'll get a menu similar to the one below, you have to copy the URL and your uniquely given Authorization code and put it into your top.gg server settings on the site.
To do this, go to https://top.gg/servers/, select your name top right (or Login if you haven't already), select Edit on your server, then scroll down to Server Webhooks and then put the URL and your unique Authorization code into the boxes.
Make sure to first click Submit, then come back and click Test Webhook to complete the setup.
If you click Test Webhook without submitting, the values will disappear and nothing will be submitted when you click Submit.
To check that the setup is complete, you can type vt!setup, react with the book and type server-topgg.
It should say "Completed". If it doesn't then try following the steps above again and click Test Webhook at the end.
Otherwise you can always join the support server here and we'll be there to help in no time.