In the related table (the "many" side), you can use the Lookup Wizard to create a field which (1) stores the "one" key and (2) shows user-friendly text. IF the text is not sufficiently useful (eg you see a Surname when you would rather see Surname, Firstname) you cna do this:
Go into Design view on the table.
Select the lookup field in the top half of the grid.
In the bottom half (the Properties section) click the Lookup tab. You can edit the RowSource to convert the Surname to an expression showing the full name instead.
Note: this will create a relationship between the two tables. If there is a pre-existing relationship, go to the Relationships window and delete it. You can then set referential integrity on the new relationship and you should be ready to go.
Now, when you drag your lookup field onto a form, you will automatically have a combo box. Voila!