In source view, add in the code for your SVG image. If you only have the image file, open it in a text editor to see the code.
Paste that code into the source of your topic.
Add a class, in these examples two classes have been added and applied. Open the default.css to see .fa-svg-blue and .fa-svg-red.
Note the attribute in the CSS fill: currentColor; By applying that attribute in the CSS rather than in the code for the "image", it is not necessary to add it the SVG code if it is not already there.