You won't exactly miss it! Mount Teide rises 3,718m above Tenerife and sits almost bang in the middle of the island, inside Teide National Park. If you're looking up the Teide location before your trip, though, don't navigate to the summit. Unless your car has suddenly developed mountaineering skills, that's not going to work.
For most visitors, the useful Mount Teide location to save is the Mount Teide cable car location on the TF-21. This is where you'll find the lower cable car station and the main Mount Teide car park.
Address: Mount Teide (Find on Google Maps here) | Mount Teide cable car base station location (Find on Google Maps here)
Nearby landmark: Roques de García, inside Teide National Park (Find on Google Maps here)