Instructions for installing and deploying the list form apps. You should first try this within a test site.
App Catalog
The list form app templates are developed with the SharePoint Framework and need to be deployed to the SharePoint App Catalog, https://docs.microsoft.com/en-us/sharepoint/use-app-catalog?redirectSourcePath=%252farticle%252fuse-the-app-catalog-to-make-custom-business-apps-available-for-your-sharepoint-online-environment-0b6ab336-8b83-423f-a06b-bcc52861cba0.
Upload solution to app catalog
Go to your site’s app catalog, https://YOURSHAREPOINTAPPSURL/AppCatalog/Forms/AllItems.aspx.
Upload or drag and drop the PACKAGENAME.sppkg (e.g. fast-change-management.sppkg) to the app catalog.
This deploys the client-side solution package. Because this is a full trust client-side solution, SharePoint displays a dialog and asks you to trust the client-side solution to deploy.
Trust client-side solution deployment.
Select Deploy.
You can see if there are any exceptions or issues with the package by looking at the App Package Error Message column in the app catalog.
Add app to site
Now we need to add the app to a SharePoint site.
Go to Site contents and click on add an app
Search or scroll to find the app you want to install. Our apps usually start with FS (e.g. FS Change Management).
If everything goes well, then the app will have deployed any lists and or webparts included in the app.
Replace list forms
Now that the list forms app has been successfully installed and added to a site, it’s time to add the new webparts to the newly created list’s new, edit and display forms. Go to SharePoint form customization to complete the template setup.