The way I did it was to let kwiziq take the lead. Step by step you will first learn to recognize the verb forms of passé simple and later you will be prompted to reproduce them actively. Besides kwiziq I also read French books (e.g., "Le petit prince") which used passé simple.
The important point to remember is that for a French kid growing up in France, passé simple is as now to him as it is to you. And it is just one other verb form, so really no biggie.
-- Chris (not a native speaker).