The spool of filament should be installed on the printer so the filament is coming off of the top side and down to the extruder as shown.

The extruder on a 3D printer, is the device that feeds the filament to the hot end. On the RMAX v3, the extruder is called the EZR Struder. It is the component on the side of the top assembly that has a clear cover, black base and red release lever.

Press the red release trigger and push filament down through the filament path on the side of the EZR Struder until you see it in the clear PTFE tube (connected to the EZR Struder)

This clear tube is often referred to as a BOWDEN TUBE. The material of the tube is PTFE

Either rotate the blue knob on the EZR Struder or press the red release lever and feed filament to the hot end until you see the filament just above the top (as shown in picture 3)