Let me give you some starting pointers to get you going in the right direction. They won't be a full "do this and it'll all work" answer, because you've started a job that you'll need to understand fully yourself if you're gonna make it work the way you want it to.
Regardless of this, think it through and post questions along the way no matter how foolish you may think they are. There are lots of newbies, and we all were newbies at some point and someone taught us to walk.
Thought #1: You imported 5 Excel Spreadsheets into 5 databases...why? You're in FMP10. Import your spreadsheets into 5 Tables which are all in 1 database.
Thought #2: If you want to link the leads to the Contacts, they have to have something in common...what is it? For example, an account may have several opportunities...these opportunities exist for this account - that's what links them. The details of the opportunity can be linked to the details of the account by relating the opportunity table and the account table.
Check out your Account ID#...looks like that is ripe for relating tables...but does it accomplish what you're trying to do?
Thought #3: when you've decided what common bonds exist, or should exist, between your tables, the "link" is called a "relationship"...look at your tables graphically under File>Define>Database and clicking on the relationships tab. Relationships must be between two fields...one field in one table and one field in another. Drag one 'to be related' field to the other table and you'll see a relationship line form. You now have two related tables. When the two relational fields match, you can access one tables data from the other table. When they don't match, you cant.
I'll stop here...I don't know if I'm treating you at, above or below your actual FMP10 skill level. What do you think?
Don't worry, you haven't offended me. Took me about 15 minutes just to figure out how to reply to your post. Thank you so much for taking time to offer assistance and suggestions. I truly appreciate your help and time. I really hope that I can gain a better understanding than I have by reading the User Guide.
RE: Thought #1: I imported five Excel workbooks into 5 different databases ... because I couldn't figure out how to import them as 5 different tables in one datebase. I'm open to suggestions ... having the 5 tables in one database should make it easier to manage. After I can get that done ...
RE: Thought #2: I'm trying to find the similarities between the different tables, but having difficulty. From the little I know about Salesforce, it is NOT a relational database (http://blogs.salesforce.com/analytics/2007/04/types_of_joins_.html). The Account ID is common between the Contacts & Opportunities tables, but not the Leads or Accounts tables. If it's only one field that needs to be in common from each table, I think I can probably find one field between Leads & Contacts (first, last name ...), Leads & Opportunities (account ID ...). Please clarify, if possible.
One more vague set of questions/comments:
From what you've written so far, it is clear you have a partially-defined need and are trying to finish defining it and to meet it with a piece of software that is highly customizable. Good choice...but is it your intent to customize it yourself from an empty screen, or do you just want the Dbase done and functioning properly so you can get back to work?
If it's the former, and you are interested in the way Dbases work and all the techie little details of it, Great! Join the club and start out by downloading some of the dbases that are availble and reading the whitepaper to get a base level of familiarity. Pull 'em apart and see what makes 'em tick.
White Paper for FMP Novices
If it's the latter, and you just want the finished product, there are a bunch of folks willing to develop a custom solution for you so you can rest easy and get back to the income generating work of relocating physicians (assumed from your signature line) ;) Some of these folks might be found among those here on the forum "i.e. FMP certified developer..."
I certainly do NOT mean to brush you off, but I get the idea that you are looking for a large quantity of start-up info and would be best served by a tutorial or introductory course rather than a forum. Please understand...I went through such a tutorial way back when and it was an awesome jumpstart into Dbases...I would want the same for you.