I followed the directions I found on this site, which was to just drape the tortillas over an upside-down bowl and bake them for 10-15 minutes (depending upon the size) in a 375° oven.
I used the unbaked tortillas from Costco and tried a few different sizes. For the muffin tins, I cut the tortilla into fourths. I liked the ones over the custard cups the best, but all of them were eventually eaten!
We also tried Cinnamon Crisps with some of our tortillas. The first few sites I checked suggested brushing the tortilla with melted butter, sprinkling with cinnamon sugar, cutting in wedges with a pizza cutter, then baking at 350° for about 10 minutes. I'm sure those would have been fine, but we went with Pioneer Woman's version which was buttering and sugaring both sides of the tortilla, leaving them whole while baking, and then breaking them into pieces once they'd cooled.
They were delicious on their own, but also made the perfect garnish for some rice pudding we had in the fridge.