Mapping additional mouse buttons (Windows 10)

I have recently got a gaming mouse to go with a new gaming laptop (the bast for Blender, I find), it’s a E-Blue Cobra Junior, and it has 2 additional buttons under your thumb. At the moment, these are mapped to forward and back on the browser, which is not great, you keep on accidentally pressing them while browsing. What I would like to do is map them to shift and ctrl, meaning I can shift-click and ctrl-click one handed.

ANy ideas how I can do this?

I run Windows 10.