Add sales information to existing clients

Hi, I have just signed up for the free version, so I'm new to this. I've been trying to figure out how to enter sales amounts for existing clients. I noticed that I can enter it under Lead, but like I said, they are existing already. I'm just going through the consolidation process, which I'm entering all the information that I already have in Zoho so I can use the "This Month Sales" report, etc. Thanks!