During your upload, before you click on the green tick sign, you will have the option to tag the child/children.
Step 1: Click on the name of the child/children that appears in the pop-up upload page (circled in red below):
Step 2: Tick/untick the child/children
Step 3: Click on the green tick sign on top right to save the changes.
If you would like to tag/untag children after uploading, please follow the steps below:
Step 1: Click on the content you wish to tag/untag
Step 2: Once the content is enlarged, you will see the 'Activity' pop-up page on the right side of your page. Tick/untick the child/children.
Step 3: Click on the 'Back' button to save the changes (circled in red below)