You can create text styles and add them to your Styleguide by clicking on the button right next to the font name.
You’ll be able to see which style a text layer matches with when you click on a text layer. Typeface panel shows the matching text style if available.
If you're working with Sketch, Zeplin grabs all of the text styles of a Sketch document when you export any artboard in it. These text styles will be listed under the “Styleguide” section of your project. To add them to the project permanently, you can either add them all using the “Add All” button or click separately on the ones you want to add.
By default, when you add a text style (either from Sketch or a text layer in Zeplin) it’ll be added with the color. Then, you can remove the colors individually as you please.
You can edit names of text styles by simply clicking on their names.