How to Open Window

Thanks for your patience during this busy season. This is an old push-bar type operator. To open the window, what you need to do is unfold it so that it's sticking straight out (you already did this part). Then, you just push.

If you're feeling resistance, then check to make sure the window isn't locked. It could be painted shut, like you said; that's common for octagonal windows since their repair parts are very difficult to acquire. Other than that, it could be an issue with the hinge. The push bar itself is rarely the problem, or at least you'd know for sure if it was the problem, since their design is so simple.