I'm trying to make part of the text for a tutorial bold. Does anyone know how to do this so it only impacts the specific text in the specific step and not all the text on all the steps?
It depends on what kind of control you are using to show the text.
For a rich text editor, use <strong>text</strong>
For html text, use <b>text</b>
In case you are using a normal label, I'm affraid that doesn't support partial bold, just all or nothing with that one.
The gallery only contains the circles, presumably to show progress in the process.
From the controls list, it seems it's the label ending with ControllerLink (that's the name used in the highlighted part of your first screenshot). You would have to replace that control with the html text control.