After the first connection to the biologic parents (pair of father & mother), You can add more connections i.e. to adopt-parents. This different status You can set in the adopted persons profile with Add parents, Attach parents or Manage parents.
To attach additional Adopt-Parents / Adopt-Step-Parents should be possible the same way. But take care about to loose the real blood line of this person. Try it
Because You entered Your questions in the Family Tree Builder forum, I assumed You are working with this program.
On the online tree, You can connect to other 'parents' with the More ... - Connect to existing person on the short profile on the left side of the browser window. Before You do this enter the adopt-parents in Your tree.
The other option is inside the profile of the adopted person. Use the Profile button on the left and then Edit profile and go to My family. There You can enter the adopt-parents.