Hey Eric,
the Onefinity Controller is a stand-alone CNC controller. This means, it is a computer. You don’t need a computer. What you need is a HDMI monitor, a USB keyboard, and a USB mouse. Or a touchscreen. In the Onefinity Controller, there’s a Raspberry Pi inside as the core.
The other way is to control it from remote. For this you need an Ethernet cable which you connect between the Onefinity Controller and the router in your house, or directly to a remote laptop.
On this remote computer or laptop in your network, you open a web browser and enter “onefinity.local” into the address bar. This works if your router or your remote computer has zeroconf properly configured.
The first thing I would try is to attach a HDMI monitor and switch the Onefinity Controller on. You should see the Onefinity Boot screen and then the CONTROL page.
Note that you did not have to assemble the machine by trial and error. You could simply follow the Owner’s manual. There is also a Controller manual under https://www.onefinitycnc.com/support.
If you don’t have a HDMI monitor, the instructions to use the Onefinity Controller from remote is here: