Here's are the steps to block ads in you tube
1. Click the AdBlock button in the browser toolbar and select Options.
2. Select Allow whitelisting of specific YouTube channels.
3. Restart your browser.
4. Open a video in a channel you want to allow ads on.
5. Click the AdBlock button again and select Whitelist (the channel's name) channel.
Best Ad Blockers for YouTube:
4. Ad Muncher.