Hello. I can't figure out how to load graphics sets like SimCity Graphics Set 1: Ancient Cities and, SimCity Graphics Set 2: Future Cities.

To modify and customize SimCity you have to use the SimCity Urban Renewal Kit (SCURK), which comes with the game (look into Window's start menu: \GOG.com\SimCity 2000 Special Edition\Urban Renewal Kit). You can download its manual from GOG's extras for SimCity. There's a description on the pages 61-62 "Using Pick & Copy - DOS".

From within SCURK you'll find the tilesets in the folder C:\SCURKART
(Actually the folder SCURKART is inside SimCity's installation folder and not under C:\ It just looks that way in SCURK because the application is running in a DOSBox environment, in which the game's folder is mounted as C:\).

"SimCity Graphics" is a pair of expansion packs for the first DOS version of the first SimCity. There's also a combined rerelease for SimCity Classic (renamed "SimCity Classic Graphics"), and separate versions for the Amiga port (both renamed "SimCity Architecture").

They are not for SimCity 2000, and likely won't even try to load.