What should I do to prepare for my kidney failure?

Excellent question. Indicates your understanding & acceptance of problem. Carry on with low protein & low potassum diet& control acidosis & salt intake for as long as you feel reasonably well. Ask your nephrologist about how long before need for kidney replacement therapy. Consider pros and cons of dailysis vs transplant. Latter is best & living related kidneys are best & avoid waiting list for cadaveric kidney.
Preparation for RRT. If you have advanced kidney disease per your nephrologist then you should consider different available options for renal replacement therapy like dialysis and pre emptive kidney transplant in addition to dietary and lifestyle changes.