Parents are already in the data base, I want to enter children who are not in the data base. On the top of the form  click check if person is already in the data base, is this for the parents? Click if the person exists, is that for the child? Do I need to enter the parents names when they are already in the data base?

It is for the child. It may be that the children already exist, but unlinked. If you find them, younpick them out of the list of potential matches, and link them. Otherwise, you can create them.

The child is not on the parents card and not listed on a card of their own, should I leave the boxes unchecked?

Which boxes? I am not sure what you mean by listed on their parents' card. There is one record for each individual. This record can be linked to the parents' records and to the children's records.

When trying to add a new record, you first have to check whether the record already exists. If so, you link it. Otherwise, you create it, and it gets linked.

The parents are in the data base, I'm trying to add a married child, not on the data base with the parents and not as an individual, I have filled in the information for the married child and now in red is ( Please verify  the person SVP) Do I check the boxes for this couple under their names?