You have a lot of ways to do that:
Console
git remote set-url origin [Here new url]
Just be sure that you've opened it in a place where a repository is.
Config
It is placed in .git/config (same folder as repository)
[core]
repositoryformatversion = 0
filemode = false
bare = false
logallrefupdates = true
symlinks = false
ignorecase = true
[remote "origin"]
url = [Here new url] <------------------------------------
...
TortoiseGit
Then just edit URL.
SourceTree
Click on the "Settings" button on the toolbar to open the Repository Settings window.
Click "Add" to add a remote repository path to the repository. A "Remote details" window will open.
Enter a name for the remote path.
Enter the URL/Path for the remote repository
Enter the username for the hosting service for the remote repository.
Click 'OK' to add the remote path.
Back on the Repository Settings window, click 'OK'. The new remote path should be added on the repository now.
If you need to edit an already added remote path, just click the 'Edit' button. You should be directed to the "Remote details" window where you can edit the details (URL/Path/Host Type) of the remote path.
To remove a remote repository path, click the 'Remove' button
ref. Support