What other nutrients are you using along with the florabloom?
Florabloom is part of a 3 part GH line of nutrients. You need to start with FloraMicro which is the foundation of the system. Then supplement with FloraGro and/or Florabloom, which to answer your next question is as soon as now if you'd like. If you have a sufficient root structure developed, they need to start being fed immediately in low doses and gradually working your way up week by week, which you can measure by the ppm's. Week 1 ppm's should be roughly 300ppm, week 2, 600ppm, ect ect.
Figure out how much water the aerogarden holds and read the table on the side of the bottle and get ready to do some math to figure out how much teaspoons to use.