Tostadas are used to add toppings to. Common ones are cold seafood dishes like "Ceviche" and "Ensalada de Jaiva" or "Carne Apache" it can be used to spread or scoop certain dips like Guacamole or refried beans, etc.
VERY SIMPLE TO MAKE.
-Fill a small pan half-way with oil. Heat on medium high. Check if it's hot enough by dropping a piece of the tortilla in if it sizzles and bubbles it's ready. Be patient oil takes like 5- 8 minutes to heat up in large amounts. You can test it with a wooden spoon.
-Put 1 tortilla in and swish it around until it turns golden on one side then flip and do the same.
-Take out salt it lightly and repeat.