My younger ones are new to Beyblade, any advice please?

My 2 boys, 8 and 6yo are new to Beyblade. They have recently indicated interest in joining tournaments.

Is there any tips or guides on how to get started?

I have registered each of their beys under one beyblade X account - right thing to do? Assuming I’m getting additional one bey each (total 4), can two of them swap in tournaments (to make up 3 beys)

Any other advices, like how to best utilize the Bey points: exchange rare beys?