You can join a token network by either:
Quick Connect lets you automatically open channels to nodes recommended by a Path Finding Service.
If you click the "Transfer" button without having any open channels for the selected token you will get prompted to use Quick Connect. Alternatively you can click the three dots on the top right of a token network view and choose "Quick Connect".
When using Quick Connect:
Enter the total number of tokens you want to allocate
Distribute the token amount between the recommended partner nodes. Only if a deposit is selected for a node, a channel will be opened.
The amount you choose when connecting is what will be available for making payments. You can always add more funds by depositing to a channel.
You are now ready to make the first payment!
If you want to join the network for a token and that token is not displayed in the list of tokens it might mean that it has not been registered.
To register a token yourself:
Click "Select network" in the tokens view.
Click "Add new network".
Enter the address of the token you'd like to register and click "Register".
You can follow the steps for Quick Connect to join the network of your newly registered token.