This tutorial will demonstrate how to use rectangular hitboxes to detect collisions in a project. Images used can be found at the bottom of this page.
If a Rectangle doesn't fit your shape well, you can use a List of Rectangles to better represent your collision zone. You can also use circular hit 'boxes' (or lists of circular hit boxes) as described in the Collisions with Circles tutorial (which I haven't made yet).
https://github.com/AldworthClass/Monogame-Collision-with-Rectangles-Example
https://docs.monogame.net/api/Microsoft.Xna.Framework.Rectangle.html
Look at the Properties and methods available for Rectangles.
pac_up.png
pac_right.png
pac_left.png
pac_down.png
hobbit_door.png
coin.png
rock_barrier.png