In what way is it not working?
Are you trying to group different weights and styles in a single family, e.g. Regular, Bold, Italic, Bold Italic and more? That’s certainly possible (most Google fonts do this), and I think you could get some clues from studying a Google font link: e.g. by pasting https://fonts.googleapis.com/css2?family=PT+Sans:ital,wght@0,400;0,700;1,400;1,700 into a browser address bar and studying the stylesheet that Google generates.
In this case, Google provides multiple @font-face definitions, so there is a separate definition for each style and weight (e.g. font-style: italic and font-weight: 400), along with a separate URL for each definition, but they all specify the same family (font-family: ‘PT Sans’).
Following this example, I think you could construct a stylesheet that specifies different weights and styles for “Admark” (font-family: Admark), so that AdmarkRegular would be a single style/weight within an “Admark” family.
If you do that, you should be able to add “Admark” to Xway’s Fonts view and set its URL to point to the stylesheet. Admark would then behave like other fonts (Times, Palatino, PT Sans etc.) in that you would be able to choose “Admark” from a Font popup, and separately choose a style (Normal, Italic) and weight from Xway’s Font Style and Weight popups.