If you're using the Joplin desktop application on Windows - you could simply download Greenshot, it's free, safe, easy but powerful.
Simply hit the Printscreen key, draw a rectangle area: the image goes to the clipboard.
Paste it (CTRL+V) in a Joplin note. You then can paste as many other screenshots in the same note, or anywhere you wish.
You can also add arrows, highlight zones or hide sensitive information, etc.
HTH.