A guide for total dummies:
1. choice - going to a computer store:
Dress up, head to a computer store, buy a better graphics card, replace your old AMD RADEON HD6570 with your new card, have fun.
2nd choice - buy a card over the net and have it delivered by mail:
Search the net for a graphics card, buy it, wait for it to arrive by mail, replace your old AMD RADEON HD6570 with your new card, have fun.