If his Roku is attached to YOUR Roku account, just add the channel to your Roku.
If he has his own separate Roku account, you'll need the password and email associated with his account to log in and add the channel that way.
Either way, the channel will be added to his Roku the next time his system updates, usually within 24 hours. If it's a channel that requires a login he'll have to do it from his end.
- Roku Streaming Stick +, 3810X, Ser YH0059427035, wifi - Samsung UN55ES6100
- Roku Streaming Stick, 3600X, Ser 5S56D8240827, wifi - JVC EM37T
- TCL Roku TV 43S425/C107X, Ser X000001R60KV, wifi