How to set up a new member as "contributor only"
Click the following link for instructions on how to add a family to the family list.
Once the family is added, select Edit Details → Select Family Group → Select Contributor Only → Save and Close.
And then when you post to them in Detail Posting, make sure your Posting Filters (1) are "Both" and "All Groups" and your Posting Options (2) says "Name" for Input By since they probably don't have an envelope number, and then you can type their last name in the Post To field (3) and select them and check the Post to Preview (4) on the right to make sure it posts to the right family:
Note: Choose the appropriate registration status and member status.