New appoinment/activity cannot be linked to an account/contact

New appoinment/activity cannot be linked to an account/contact

I have created a new Appointment and would like to link/associate this activity with an account but when I click on the search binoculus, nothing happens. Is this because I have a Free licence or this is not a feature that works in the calendar.
 
I am copletely new to Zoho and I am testing this CRM to see if it would work for our company that has 30 users.
 
Thank you
Robert