Start with the bookmarks you already have
When you install Caves of Wonders (CoW) from the Chrome Web Store, the setup process gives you the choice to import your existing bookmarks from Chrome’s built-in bookmark manager.
Your bookmarks are placed in one Imported Cave. A Cave is a top-level space for a part of your world, such as work, hobbies, or entertainment. Your existing folders become Chests, so you can keep building on the structure you already know.
Import later whenever you need to
If you skip import during setup, select the Import Bookmarks button in the right sidebar. 
This creates another Imported Cave, ready for you to organize.
Bring bookmarks from every browser
Fleet users can use Import Bookmarks in each connected Chromium browser or device to bring in that browser’s local bookmarks. Fleet sync then makes your imported collections available across your connected browsers and devices.