In Marlin you need to set your X endstop to a MAX end stop, change the -1 to a 1
You also need to adjust the pots on the stepper drivers if the motors aren't moving.
An axis may only move in 1 direction until you home that axis - as it doesn't know how far it can travel without homing first.
Also see a previous post I made re: enstops etc
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Hope this helps
Steve
My updated Instructable on our Prusa i3 Build
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