Easiest way to add SB to your project.
Install sb-cli globally.
npm i -g sb-cli
Then go to your project and run:
sb-create
That's all you've to do.
sb-cli also supports yarn. If you are using yarn, this is how to use it:
yarn global add sb-cli
sb-create --use-yarn
sb-create
will identify it's installed with yarn and it'll use yarn to install deps.
This is the way, if you wanna use yarn for all of your storybook projects.
If that's not the case, you can do this:
npm i -g sb-cli
getstorybook --use-yarn
For more information, refer SB documentation.