Thank you for your post.
When you define the relationship, make sure the numerical code in both tables are linked to one another. If you have more than one field between the two tables, then the linking will not appear until all "key" fields match up.
On your layout, create a portal (the tool just below the oval) and include the numerical code field and description field in the portal from the related table. Go into Browse mode, and enter a code that you know exists in both tables. Tab out of the Code field, and you should see the Code appear in the portal along with the description. If this isn't happening, then you may want to check the relationship again, and make sure the Numerical Code field is identical in both tables.