You need to start a new form, using the "Design A Form New From Data Connection" choice. You will be prompted to enter your Access mdb.
Make a note if the final screen of the Data Connection wizard tells you if Submit is enabled. If not, then note why not.
Now, look at the Data Source pane. You'll see your Access fields there twice. One set are Query (q) fields and the other are Data (d) fields.
Drag a query field into the proper layout table. (InfoPath creates two tables and two buttons automatically.)
Next, drag your data fields into the other layout table.
Preview the form and put something you know belongs to the db in the query field text box. Then click Query. You should see the appropriate data in the data field text boxes.
A further refinement is to create, in Access, a query that returns just one field. Set that up as a secondary data source, then change your query field text box into a drop down. Use the secondary data source (the one-field query) as the source for the drop down. Next, set a rule that when that control (the drop down) changes, query the main db connection. That way you'll present the user with a list of appropriate choices, no guess work, and the db will automatically query after a choice has been made.