How to Manually Sign In to a YouTube Account
You must manually sign in to your YouTube account if you don't get logged in automatically. When must you manually sign in to YouTube? Well, if you register with YouTube on your home computer, the next time you visit the site using that computer you’re automatically logged in under your username. But if you go to YouTube from another computer, you aren’t logged in automatically.
Logging in manually is easy.
Go to YouTube.com
If you just want to view some videos, you can do so right here — without logging in to your account.
Click the Sign In link at the top-right corner of the page.
Bam— the Sign In page appears.
Type your username and password.
Forget your username or password? Don't worry — YouTube has handy help links right under the Sign In button.
Click Sign In
You’re now logged in to your YouTube and can take advantage of the features that only registered users can access.
When you register an account with YouTube, YouTube automatically downloads a cookie to your computer. YouTube uses the cookie to identify you whenever you return to the site using the same computer. It's the cookie that helps log you in automatically each time you visit the site. You know that you’re logged in because your username appears in bold at the top of the page.