There are two ways to do it:
go to your YouPHPTube dir and type git pull
cd /var/www/html/YouPHPTube/ && sudo git pull
In the simplest terms, git pull does a git fetch followed by a git merge.
You can do a git fetch at any time to update your remote-tracking branches under refs/remotes//.
This operation never changes any of your own local branches under refs/heads, and is safe to do without changing your working copy. I have even heard of people running git fetch periodically in a cron job in the background (although I wouldn't recommend doing this).
A git pull is what you would do to bring a local branch up-to-date with its remote version, while also updating your other remote-tracking branches.
Some users some times change a file, and can not do a git pull command, usually they get this error:
... Please, commit your changes or stash them before you can merge. Aborting
the solution is to force to overwrite your files, you can do this command.
git fetch --all && git reset --hard origin/master
Check this video to know how to do it: https://tutorials.youphptube.com/video/force-git-to-overwrite-files
Use your favorite file transfer to download a master copy of YouPHPTube and upload it to your site.
Unzip it and replace all files in your YouPHPTube-root. Do not clear or replace the videos-folder.
Remember, always check your YouPHPTube menu -> Update version to run a script update. Never skip a version!