Installing RetroPie through Raspberry Pi's OS (Raspbian) and also enabling Playstation 1 Emulator in RetroPie. I'll also teach you how to write images on your Mac or Windows PC as well (no worries ).
Use our retro pi guide for Raspberry Pi 2 B+ Models as there is no really difference other then hardware (faster)..
Also, if you've just gotten your Pi, you might be interested in some of the things I bought for the Pi and why I bought them. I discuss a lot about the items I bought for my Raspberry Pi. If you're interested, you can click here. It's good to have these things if you want to be able to overclock without any worried as well.
Click here to visit petrock (retro pi) website
Click here to visit my post, easy step by step guide to setup the retro pi
Here's What You'll Need
Raspberry Pi (Obviously)
Video Cable (Preferably an HDMI for sound, but HDMI to VGA/DVI if you really need to, but you'll need speakers for the audio jack)
Micro SD Card (Preferably 8gb or more, but 32gb sells cheap, and Samsung read speeds are the fastest)
Power Supply (Micro USB Cable and Power Brick)
SD Card Reader
Here's Some Optional Stuff (but highly recommended)
Game Control Pads
Heatsinks and Ventilation will really help you out since you're gaming and video output takes a lot on chips. Also game pads will help better your experience with emulators for that classic controller feel