M6 is tool change. At the start, put in:
M6 T1 (for tool #1)
Then, for the second tool, put:
M6 T2
In General Config, top left corner, under "Tool Change", selet "Stop Spindle, Wait for cycle start". Mach will stop and let you change the tool, then continue when you press start. On one of the screens, you can set the tool change location that it will go to and wait for you to change tools.