Yes, you can use your own custom fonts with UltimateWB.
The fonts shown in the Styles Manager dropdown are the standard font choices, but you aren't limited to those. You can add a custom font using CSS and the Code: Please login/register for access rule.
The basic process is:
Get the web font files for the font you want to use (ideally WOFF/WOFF2 versions).
Upload the font files to your website.
In Configure Site > Styles Manager, add the Code: Please login/register for access CSS in the appropriate Extras section.
Then specify that font wherever you want to use it.
For example:
Code: Please login/register for access
Then you can use Code: Please login/register for access where you want the font applied.
You can also apply the font directly to an existing section through the Extras area in Styles Manager. So, for example, if you wanted your custom font used for the Header, you could add:
Code: Please login/register for access
One nice thing about doing it through the Styles Manager is that you can change the styling centrally rather than having to edit every page individually.
We have a more detailed step-by-step explanation here:
How can I use a Custom Font on my website?
Also, you don't need to know CSS for the normal Styles Manager options - UltimateWB generates the CSS for those settings. The custom CSS option is there when you want to go beyond the built-in choices.