The out-of-the-box editing experience is a little hard to use in my opinion... and most others... Not only is there no 'Dark Mode' switch built in, but even the font is hard to read. Exhibit A, the below screenshot.
This is super easy to set up, but not quite the simple checkbox that I would want it to be. Here's what my VBE looks like. You can see not quite everything is dark-themed. The toolbars are still light even with these settings applied.
Click on Tools, then Options:
Then this pop-up should appear:
All you need to do is edit each line item in the Code Colors area, using the Foreground and Background color dropdowns. This is also the area where you can change the font size and type if you so desire. If you want to know my preferences, see below, I took a screenshot of each item.
Here are the settings I use. Feel free to copy.
Normal Text
Selection Text
Syntax Error Text
Execution Point Text
Breakpoint Text
Comment Text
Keyword Text
Indentifier Text
Bookmark Text
Call Return Text