To copy your Figma sections and paste them into Bricks builder, select a section and in the Plugin UI click copy.

An alert will appear at the bottom of the screen indicating that the section has been copied.
Then go to Bricks Builder and paste the section into the editor.
Remember to enable the paste option in your browser. If you still don’t know how to enable the Bricks copy and paste function you can watch this video (This feature only works if your website has an SSL certificate):