OK. I'm no expert, but 915resolution seems pretty simple. First, it only works for some Intel processors, but you may have one of those.
If you use Appbrowser to "Install" it, it should be loaded automatically the next time you boot into Tiny Core (assuming that you have some form of persistence). If I remember correctly, you may have to select screen resolution during that boot, but then the chosen resolution is "remembered." (In earlier versions of Tiny Core, I believe that choosing to "Mount" it from Appbrowser worked well.)
That's all there is to it--at least in my setup.