Flashing Ramps 1.4 guide

Just wondering if anyone has a guide or better still could walk me through flashing the firmware onto a ramps setup? Where do i get the power for the board from? Do I plug the round connector from my supply into the round connector on the mega 2560 to supply it with power while flashing? obviously i know that it needs connecting to my computer via usb.

You should only need to connect the mega 2560 to your computer using the USB cable - no other power is needed. Arduino.org has a pretty good set of instructions on how to do it, the basic steps are listed at Getting Started which has some links on how to install the IDE for Windows and Mac as well as the links to board specific instructions.

Step by step with pictures.

https://www.v1engineering.com/marlin-firmware/