How to add existing project to existing solution in TFS ?

Source Control -> Right click on solution folder -> Add Items to folder

How to remove repository in TFS Online ?

1. Navigate to: https://{your_account_name}.visualstudio.com/DefaultCollection/_admin
2. Choose your repository + right click + choose delete

How to force file update in TFS ?

1. Find file on drive and replace it with a new version

 2. Open Team Explorer -> Source Control and find it in archive
 3. Click right on file and select "Check out for edit"

4. Confirm changes as shown..

5. Now TFS knowsthat file needs to be updated in repository

6. Check In pending changes