CRM setup

CRM setup

Hi
I am really new to this CRM so would welcome advice on setup please. I am a funeral minister and require all my clients/contacts and leads to be on the system. 
My business is simply in that I have funeral homes as my customers, within my customers I have their clients to attend to (the actual family of the deceased), and I also have new potential funeral homes I want to deal with (presumably these would be 'Leads"?)
Before I go entering data like a mad man I just want to get the system right at the start 
So my question is on structure - who is a client? who is a lead? and who is an account?
Thanks
Tony