I opened the dxf in CAD, exploded the lines in the letter "A", deleted the lines in green, save the Dxf.
1. Import dxf into LC
2. Select Mill Module
3. Clean and turn off rapids,
4.You can select the same lines in " A" and delete them in LC ( probably quicker in CAD ) to clean up the text.
5. Open LAYER menu, pick or create a tool ( sen to all layers ) , then define Cut parameters ( send to layer )
6. Post code to Mach3 Mill
The picture on the bottom shows the file in Mach3. Note the extra rapids in letters like P, R,Q and the extra lines are actually cutting paths. So if you want to cut the just the outlines of the Text, suggest you clean them up.
Basicaly all in the manual.

PS: took longer to type this than from LC to Mach3

RICH