We've worked hard to create a CPU and battery friendly image for the Pocket Pi FE, balancing performance with overall power usage. You can find the download in the releases section. Thanks for supporting the Pocket Pi FE.
The Pocket Pi FE uses the newly developed One For All software which handles the everything from the battery monitor to the controls. It's constantly being developed and if you do find any issues please don't hesitate to raise them on the One For All github, or if you're not sure if the problem is related to that software, on this repository.
After this is done, simply pop the micro sd card into the Rasbperry Pi and turn it on!
If your card is bigger than 8GB, you will need to expand the image. This simply means allowing Retropie to use the full size of the micro SD card instead of just 8GB. There is a brilliant tutorial here / https://www.youtube.com/watch?v=TeogvADiZkQ