Is it possible to use GitHub Desktop application to commit to a Bitbucket repository?
If yes then where I need to add in GitHub? I see "Clone in Sourcetree" option, but I want to clone in GitHub Desktop. Is it possible?
If what you want is using Github App for pushing your code to Bitbucket what you need to do is going to "Settings" (in your local repo) and change your Primary remote repository (origin) to point to Bitbucket in your Github App. Then you can Sync Branch.