IMPORTANT:
Before you install any apps you must make sure your SP2019 server is properly configured to host apps, by following the MS documentation: https://docs.microsoft.com/en-us/sharepoint/administration/configure-an-environment-for-apps-for-sharepoint
Installation steps can be found below:
1. Download the Apps Package zip file and unzip it on your desktop.
2. Install and deploy the KWizCom Apps Foundation Full Trust.wsp package using the PoSH
script from the extracted zip file or by using the standard SharePoint Add-SPSolution and Install-SPSolution commands
3. Upload packages to your Tenant app catalog
a. As a Farm Admin, go to the “Apps for SharePoint” library in your Tenant App Catalog site.
b. Upload the kwizcom-modern-apps-upgrade-onprem.sppkg package from the extracted Apps Package zip
file. After the package is uploaded you will see the following popup:
Click on the “Deploy” button to properly deploy it.
4. Go to your site and add the KWizCom Modern Experience On Prem
a. Go to the site where you want to have the app and go to “Site contents”
b. Click “New” menu and select “App”
c. Click “From Your Organization” link on the left side:
5. After the KWizcom Modern Experience On Prem has been added to your site, you can now activate the KWizCom modern apps in the relevant sites. Please refer to "installing KWizCom modern apps in your SharePoint 2019 site"