The sheer number of opensource projects out there for both Bootstrap and AngularJS is incredible. The great thing is that these can be contributed to by anyone—even you! If you find a bug, report it, or if you know how to fix it, submit a pull request and become a contributor.
Naturally, not every problem will already have a solution there for you to find. Now that you know how to use both frameworks, it's your turn to build something awesome and have fun.