Via the extension
You can import existing bookmarks from your browser with the WebCrate browser extension.
After it is installed and configured (instructions), right click on its icon in the toolbar of your browser and select "Import existing bookmarks". A new page similar to the one below will open:
It will list all of the bookmarks found in your browser.
You can select an entire folder or indivdual bookmarks you want to import. Once you are happy with your selection, click "import selected" to start the process. It may take a few seconds to complete. A new crate will be created for each of your folders containing the selected bookmarks as links.
If everything completes without any errors, head over to your WebCrate instance and view your links!