abf only puts things on abf server. To push changes on github you may use git command. Also note ABF is mainly a storage server for source files while github repository contains all the other useful stuff to build a packages.
The first time you use git you have to set you name and your mail according to the ones you use on github (otherwise the name of you local user will be used)
git config user.name <your-name>
git config user.email <your-mail-address>
A complete list of your configurations can be obtained with the following command:
git config -l
To push you changes into your github repository you may use the following commands:
git add <files-you-modified>
git commit
git push
You may use TAB with gti add to get the list of the files you modified.
The first time you make a commit in a branch you should do explicitly, so, for instance
git push origin master # first push on master branch
git push origin 3.0 # first push on 3.0 branch
To switch from one branch to another you may use git checkout. For example
git chechout 3.0 # switch to 3.0 branch
git chechout master # switch to master branch
You may use -b option of git chechout to create a new branch if it doesn’t exist already.
For pull requests you may refer to github help. On the opposite the help claims, usually there is not need to create a new branch for a pull request.
For a complete guide about git you may refer to Pro Git book (there are also localized edition) and for quick reference you may use this. For a very simple introduction you may look here. Git Magic is another translated quick guide.
For a guide about abf you may refer here, but bring in mind there are some differences between ROSA and OpenMandriva so not all commands described there are usable with OpenMandriva.
I hope this may help you a bit. 
