How do I add an image to an HTML file?

I saved an image to my computer in a folder called “images” and then tried to add it to an html page using the img tag (<img src="images/app.png" alt="problem">).

When I do this, it cannot find the image, and instead posts the alt text. When I try using images from the internet, it works fine, but when I try to reference images saved on my computer, it doesn’t work. Only potential problems I can think of are that there more than than 1 folder called images on my computer, or that I need to put something more in src (the images folder is in another folder, in the documents folder). Anyone have any idea what I am doing wrong?