Yes, the Galaxy S8+ has an SD card slot. The SIM card and SD card share the same tray, which can be accessed at the top of the phone. You will need the included SIM tool or a paper clip.

1. Push the SIM tool or paper clip into the small hole top edge, opposite the headphone jack
2. Once the tray pops out, use your fingers to pull it all the way out
3. Place your SD card in the tray
4. Push the tray back into the phone
5. That's it!