You'll need to use 3rd party software that can map those buttons to do what you like. I use SteerMouse myself... great piece of software.
www.plentycom.jp
Thanks Rod, I was just about to ask what software they recommend to use with that Mouse and I didn't see any link to download anything from their site which strikes me as a bit odd.
I've just recently ended up using Steer Mouse.app myself due to my iMac's incompatibility with Logitech's updated Mouse hardware and software but I don't know if the OP's new trackball mouse is supported.
At least they support a full 30-day free trial, but their button labelling could be a lot better then it is but their support is excellent and fast.
plentycom.jp
Finally my replacement Logitech mouse has finally started working and stayed working for a week now the way I want it. Getting a third-party Mouse to work properly should not be such a hassle on a Mac. It used to be a simple straightforward cakewalk.
Did I really miss the fact that Nulea doesn't even mention that a mouse driver would be needed, and no mention of where it could be downloaded from, or am I going completely blind.
I think I would be inclined to look at other mice myself with that kind of so-called support. But that's just my opinion.
One shouldn't have to spend another $20 for software, after purchasing a mouse to be compatible and used with a Mac.
I actually ended up having to spend another $20 for Smart Scroll, on top of the Steer Mouse price, and I'm really p'eed off with Logitech and their hardware and software changes, but that is also due to the fact that I am using older Mavericks Mac OS 10.9.5 software version.
I hope things work out for the OP.
- Patrick
=======