Adding C:\Program Files\Git\usr\bin to the PATH environment variable.
Add it manually or I believe you could run this in cmd:
set PATH=%PATH%;C:\Program Files\Git\usr\bin
updated from @Ygor Thomaz’s comments
or (64 bits)
set PATH=%PATH%;C:\Program Files\Git\usr\bin
If this doesn’t fix your problem, go through :
Get SSH working on Vagrant/Windows/Git