Do you have a RAMPS board and the rest of the electronics (stepper drivers)? You'll need to plug the RAMPS board into the mega, plug the jumpers in to enable micro stepping and plug the stepper drivers into the RAMPS (make sure you get the orientation correct and and then wire it to your printer. Take a look at the wiring guide on the wiki: [
reprap.org] and do a google search for RAMPS 1.4 setup - you'll get links like this video [
www.youtube.com].
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3DKarma.com] - suppliers of quality, affordable 3D printer kits and filament for the UK market.