To add new pages to your Figside website simply add new pages in Figma!
Duplicate your homepage and design your new page like you want (always with the Auto Layout feature in mind):
In Figside refresh your website, you should see a new page in your toolbar:
Go back on your Hompage in Figma, select the frame where you want to add a link, start the plugin and choose your page in the Navigation panel:
In the same way you can also add a link on the home link in your menu.