Hi Hiroshi Igarashi,
We cannot use the components built in Figma. we can only create components in mendix and apply the CSS code from figma to those Components.
The usual way to go is to open the Mendix Atlas UI KIT in Figma (you can find the UI Kit on Figma pages, just google the name). In the UI kit, you create a new page and start designing. You use assets from the kit so your design fits Atlas in Mendix. After the design is done, it is best to create UI Resources Package (UIRP) in your Mendix app (see the Mendix docs). That is just a special module where your "theme" will be stored. In the UIRP you create your page and popup layouts and start designing by creating page structures and SCSS. You also change how Mendix widgets look by using SCSS.