Okay. And just let them grow wild, nothing else?
No you are going to have to rewire them every year or two just as the wire starts biting in.
As they grow, they will need new wire on the new growth and movement/shape put into them.
You'll also have to prune once in a while but Id wait to really do that until they get a bit more growth on them unless its a branch or something you know wont be in the final design. Its a balancing act. If you prune too much or too soon, youll slow down the growth you want in the trunks to get them bigger. You have to learn when pruning is good for the development of the tree and when it isnt.
@Shibui gives a good example of developing junipers.
I understand this can all seem overwhelming and not knowing what to do.
The good thing is you have time to learn!
Keep reading about how we grow and develop bonsai.
There are lots of juniper threads here
Ask questions. Youll get there eventually, we all do