The best tutorial would be to locate the retropie foundation website, find a supplier for the Raspberry Pi Model 2, order it- and then try again with image 2.5.
I’ve messed with just about every setting I could to try and get the Nintendo 64 games working on the B+ and could never come up with satisfactory results. I had to come to the realisation that the processor on the B+ just isn’t quite up to snuff for N64 emulation.
This can give you some ideas to start with though. Maybe you’ll figure something out that I didn’t.