Yeah, the installation instructions that come with these kits are so simple-minded and info lacking that they're not worth the paper they're printed on. But that's the way it is with all vendors, not just yours. And I suppose those instructions are produced by the manufacturers, not the vendors.
A few of these vendors have much better online instructions, but I've forgotten which. But it shouldn't be hard to find.
But don't worry; these happy time kits are, deep down, so simple that you can learn, and commit to memory, everything that you need to know eventually. So relax and learn what you need to. You'll have a great time.
I'll bet most newbies aren't riding the day after they receive their kit. But I think most are riding a day or two after that, and feel that they have the most important bugs worked out a day or two after that. Not so bad.