[Help] - 4/8 GB of RAM detected (AMD)

Hi,

I went into About Mac this morning and found that only 4 GB of ram were detected, even though I have 8. I've done some Google-ing and found a solution for this, but they are doing it on an Intel PC running El Capitan. I'll link the guide below.

This is the guide - https://www.youtube.com/watch?v=7BMWWKlx7Uo

I could really use some help with this.

Thanks,

-Cameron