Infinite SEO: keywords

I am trying infitie SEO.

2 questions

1. I can only find a paid subscription to the SEO service you recommend in step 4. It is free for 30 days and then automatically swicthed to 99 $ a month....
I am not saying this is a bad idea, but I woulkd like to have soem more explanation on why I shoud spend 99 $ a monh on this service, rather than on one of the many alternatives...

2. In step 5, I am invited to generate keyword links automatically, but I have not entered any keywords in infinite SEO. How does the plug in know what my keywords are?