After activating of your theme, a notification will appear on the top of your screen just under the navigation in your Dashboard, inviting you to activate the plugin. Click on ‘Begin installing plugins‘
Then you will be able to active them all by clicking on ‘Begin activating plugins ’ in the info box.
It is advised to install the required plugin, especially if you want to import the demo.
If you missed the info box you can find all the needed plugin in Dashboard > Appearances > Install Plugins