Read the modding.pdf in the docs folder. It should tell you what you need to know. You should know that this whole bit about not having the manual is going to probably bite you in the backside, because copies without a manual are pirated ones. If you by some chance managed to buy an eBay copy from somebody who did have a legit copy, there had better be a way to actually verify the original sale or you will likely land in very hot water.
If you want to load a pretender that you previously created and want to make some changes to it: That's not possible in the game at the moment. You have to redo it from scratch.