Step 1:

~/project $ git init
~/project $ git add .
~/project $ git commit -m "first commit"
~/project $ cd ~/Dropbox/git

Step 2:

~/Dropbox/git $ git init --bare project.git
~/Dropbox/git $ cd ~/project

Step 3:

~/project $ git remote add origin ~/Dropbox/git/project.git
~/project $ git push origin master