Hi Orlando,
There is no Leads table in Method, a lead is essentially a specific Entity type, you would import leads into the customer table.
The only required field in the Customer table is FullName(But you have to import it into the Name field). When importing your list make sure to add 2 extra columns for Entity Type and IsLeadStatus. You will want to set the Entity Type to be Customer Lead and the IsLeadStatus to True, doing this will make sure that the leads get imported as leads.
If you haven't already I recommend watching the webinar on the import/export tool found HERE
-Michael