On purchasing the PortalXpand plugin, you will get a zip file.
Click on the Settings icon given on the right side of the title bar. Then click on Advanced Settings. 
Now, Navigate to Settings -> Solution.  Click on ‘Import’ to upload and install. 
Click on the Browse button and choose the Package Zip File for PortalXpand from the Import Solution Window. Click on Next for further processing. 
Once you import the solution, it will be displayed in the solutions grid view. 
Once you install the package, log in to PortalXpand and you must configure CRM Authentication to start syncing the data with Dynamics 365.