When you apply for an Official Artist Channel, the form asks for the channel ID of your own YouTube channel and of your Topic Channel. A channel ID is the code YouTube uses to identify a channel. It starts with UC. Paste the ID itself, not a link or an @handle.
Find your own channel ID
In YouTube Studio, go to Settings, then Channel, then Advanced settings.
Copy the Channel ID.
Find your Topic Channel ID
Search YouTube for your artist name followed by “- Topic”.
Open the channel.
Copy the ID from the web address. It’s the part that starts with UC.
Copy an ID from the channel page
Go to the channel on YouTube and select Links. It’s usually under the channel name and description.
Scroll to the bottom of the pop-up and select Share channel, then Copy channel ID. If you don’t see Share channel, keep scrolling past the channel description and social links.
When you have both IDs, paste them into the form. If you’re still stuck, contact support.