Copper Tube can be cut with a hacksaw: a fine toothed blade is best, or use a tube cutter. Do not use too much pressure on the cutting disk.
Clean the ends of the tube with a file or de-burring tool, inside and outside.
The parts of the joint can be laid out like this before assembly.
Slide the copper tube into the CTA compression fitting until it stop against the fitting’s inner shoulder. Tighten the cap nut by hand, ensuring that the tube stays firmly against the fitting’s inner shoulder.
Tightening the pipe joint
Following hand tightening of the cap nut, tighten with a spanner until the copper tube is difficult to rotate in the compression fitting, thereafter tighten the cap nut through half turn. Inspect and pressure test the joint pipe.