You would find the "Consulting practitioner" field along the bottom of your consultation notes:

To add a user to the "Consulting practitioner" field, please go into your Settings page and go to the Users tab.

Select the user you would like to appear in the "Consulting practitioner" drop-down list:

Kindly ensure you have checked the tickbox Is this user a practitioner for this user:

Now please scroll down to the bottom of their user profile, and check the tickbox Allow others to write consultations on my behalf :

Please ensure you have also clicked Save to update these changes.

This user will now appear as a "Consulting practitioner" drop-down option in your consultation notes: