Good news is you don’t need to be on the internet.

A few photos of the machine and controller would help for background info. It might need the dip switches setting for micro steps, or if they have already been set by the seller then read them off so the later ‘steps per’ value can be worked out.
I’m away from my machine and it was too long ago to remember all the settings pages in Mach3. These are the little white switches on the motor drivers and could be inside a larger box.

There are quite a few settings to enter to get it all working. Ports and pins are for the inputs and outputs, steps settings for the motors with accel decel and top speed, plus a few other settings like the kernel speed.

You sound like you are starting out so one way would be to photograph each screen in Mach 3 and post them here and the collective forum can advise on starter values for each item on each page. Once you are there and it moves you will quickly get the hang of a few key ones to tune the motors how you want them.