I want to add our trees together
I understand that you want to add your husband and his family to your family in Family Tree?
If your husband and his parents and grandparents are living, you will need to create a new record for each of them.
This will then connect them to his relatives who are deceased, and so your husband's line will become visible to you. These entries will be in what is called, ‘your private space’ - only you will be able to see or edit them.
Living people will often have several ID numbers, where they appear on the trees of different family members.
If your husband is deceased and if you know his ID number, enter it, then your husbands' details will populate. As you accept this as correct, your husband’s tree will populate too, showing his deceased ancestors who will then be visible to you.
Please study this article about living spaces in Family Tree, and also the other linked articles.
I hope that this will help you.