In your guide, select 'Add Box' (at the bottom of the Side Nav menu on the left).
Leave the box name blank.
In 'type', choose 'Profile'.
In 'position', choose 'Bottom of the column'.
Tick the checkbox for 'Floating box'.
Select 'Save' and your profile box should appear.
By default, it will show the profile of the guide owner. You can change this by selecting the cog towards the top right of the box, and choosing your preferred option.