Hi @briannenshaw071, you should be able to copy/paste the name (as long as it's spelled and formatted the same as the user profile) from the single-line text to the user field.
If you're asking to translate names in the single-line text field into names used in user profiles (for example, if the single-line text field only includes first names and you need to correlate them to their full names for the user field), you'd likely have to use a switch formula and relate them 1:1 (this could be burdensome depending on how many users you have).
Ultimately, more context may be needed in this case.