Important disclaimer: Starting with ShortPoint version 7.1.5.xx (New Upgrade), you can no longer create multiple site collection app catalogs and install different ShortPoint versions into them. You still can upload the ShortPoint app to the site collection app catalog to control who can add and install ShortPoint in specific site collections. 
For more information, check these solution articles:
● ShortPoint SPFx New Upgrade for Office 365 and SharePoint 2019
● How to Control Who Can Add ShortPoint SPFx App to the Site
● I cannot test the new release on the site collection that uses Site Collection App Catalog? What for can I use it then? 

This article will explain how to set up the Site Collection App Catalog on your Office 365 SharePoint Environment, so you can add ShortPoint SPFx to it after.

You can also set up Tenant App Catalog instead of Site Collection App Catalog. (Which option is good for me?).

Prerequisites

1. You are a Global Admin in your Office 365 tenancy 

2. You have configured Tenant App Catalog (Required)

Step 1: Download & Install Required Software

The following Software is used to connect to your SharePoint Online via PowerShell:

Download and Install SharePoint Online Management Shell

https://www.microsoft.com/en-us/download/details.aspx?id=35588

While installation, and if you get an error "This application requires the following to be installed: - PowerShell 3.0"

Then you have to Download and Install Windows Management Framework 5.0

https://www.microsoft.com/en-us/download/details.aspx?id=50395

Step 2: Open SharePoint Online Management Shell

Open SharePoint Online Management Shell

Step 3: Connect to your SharePoint Admin Portal

Type the following command to open connection: 

Connect-SPOService

Hit Enter

Enter the Url for your SharePoint Admin Portal (not your site, not yet): 

Url: https://your-domain-admin.sharepoint.com

Replace with your domain

Hit Enter

Sign in

It will ask you for username and password for the user who has permission to manage SharePoint from SharePoint Admin Center.

Step 4: Configure App Catalog on the Site Collection

You need to select the site collection you want to set up as Site Collection App Catalog.

Type the following command to get the instance of the site collection:

$site = Get-SPOSite <Site Collection Url>

Site Collection URL should be like this for example https://your-company.sharepoint.com/sites/site-collection-name

Hit Enter!

Then type the following command to configure the app catalog on the site collection:

Add-SPOSiteCollectionAppCatalog -Site $site

Hit Enter!

Step 5: Verification

Once done with steps above, you should see the following in Site Collection Site Contents:

In classic view:

NEXT: Enable Scripting Capabilities (Required Only If you want to use ShortPoint on Classic SharePoint pages)

OR

SKIP TO: Upload ShortPoint to Site Collection App Catalog