Setting up controller, auto save/exit on mupen64plus-gles2rice-highres

[CharlieC]

Hi, i'm relatively new here, so apologies if this point has already been tackled. I've tried looking through the posts and the wiki.
Using version 4.3
model 3b
using N64 emulator mupen 64plus-gles2rice-highres.
controllers snes 8bitdo
n64 usb retrolink.

Discovering retropie has been so joyful so far, although I must admit i'm close to giving up on the N64 emulation, and just accepting 8/16 bit gaming until a new raspberry pi is released.
The gles2rice-highres emulator makes the games I want to play look fantastic and I simply can't use another N64 emulator after seeing how sharp things looks with this emulator. The others are like looking through frosted glass after using this. The problem is I'm trying to set up my retrolink n64 controller, create an exit key (L shoulder as select?) and enable an auto save/load, but without Retroarch I simply don'thave the skills to do so.
I have configured the retrolink controller through emulation station, but obviously that doesn't transfer through to this particular emulator.
Any help on this would be appreciated and if you could include screenshots to keep me right, even better.
Help needed.
Thanks

[mitu]

The input configuration for Mupen64Plus is kept separate - this is documented at https://retropie.org.uk/docs/Nintendo-64/. Look for the sample configurations, there is one even for the N64 usb controller.