You can elevate a member of staff to admin permissions in one of two ways.
The first option is to find them in the organisation chart and click on the cog by their name. From here, you can simply tick the 'admin' box and save the change.
Alternatively, head to their profile and click on the cog in the top right corner of their profile header, then select 'make admin'.
NB: Note that only admin users can change admin permissions.