- Select a theme that you want to apply into the SharePoint.
- Click Review to check the product pretended to install.
- Install to open a modal with specific information about the installation.
In the target options information select classic and/or modern options. On Modern Solution you can choose where it will be deployed Tenant App Catalog or Site Collection.
Classic solution are not available to install on a Modern Site.
These options are only valid for Modern Solutions:
- Tenant Wide - It'll install at the APP Catalog Global the solution.
- Site Collection - It'll install at the APP Catalog of Site Collection the solution. If that doesn't exist, it'll try to create this feature on your SharePoint site.
For more information about APP Catalog option check the link.
For more information about step 2, follow the link. Note that you can always edit those option afterward.