The third step!
The first thing to address is the built-in seats that came with your kayak. It might need some lumbar support, but the bigger issue is the lack of cushion for your backside!
In the above video, I take you through the steps to install two different easy solutions to add cushions to a stock kayak seat. Basically, a few cable ties will give you all the hold you need to install a seat cushion. But, there is a trick when you use a stadium seat to make sure it does not pull loose.