Importing Data from Access into my combo box

Hi Everyone, I'm relatively new to access and have no idea where to start. Basically I am making a name database,
So I have a simple Access database with a bunch of first Last names and first names.
In an excel worksheet, I have 2 Comboboxes within a userform.

I want the first userform to show all the last names, however, there are many repeats, such as Smith, John; Smith, Robert; Smith, Jack
I want 1st combobox to only show distinct cases, so only 1 option for Smith will be available

When I click on Smith in the 1st combobox, I want the 2nd combobox to name all the people with the last name Smith..

How do I go about doing this? Thanks so much for your help!