How to set extra mouse button

How do I set an extra mouse button as a key from my keyboard. Example, I want mouse button 5 (a button on the side of my gaming mouse) to be the keyboard key 5

Can I bump this.

Normally you use the devices software, perhaps through control panel or it may be an icon in the systray on the far right of the taskbar.
If you've never installed specific software, now would be a good time.

No software came with the mouse. The system tray displays nothing and the control panel settings for the mouse are the same as default.

Try this software. Not sure if it will do what you want but it might. AutoHotkey - Free Mouse and Keyboard Macro Program with Hotkeys and AutoText

Stephen