The instructions are here:
This release optionally prunes the blockchain by dropping no-longer-needed information once it is processed and verified by your node. This reduces both memory and storage requirements, and perhaps more importantly reduces the rate at which both increase over time. With pruning enabled, the daemon continues to function as a full node on the network in nearly every way. I will be posting a FAQ to answer some other questions about the details of the pruning functionality.
It was released as a testing version and has some limitations involving rescanning of old wallets (click through and read including the FAQ a few posts after that if this applies to you). Other than that, no problems has been reported in over a year, so it should be fine. The branch has been updated with some patches keeping it in sync with the latest release from master.
@smooth, will the Aeon port of the XMR GUI be easier than the BBR port?
Which one will require less user RAM in your opinion? Which port will require the most modification?