These are the steps to place your parts or add parts to library into Altium Designer.
Note: Your Altium must have the latest SnapEDA Plugin for Altium. You can find that here.
Open the SnapEDA Desktop App
Search for the part that you want
If the part is available, click the part
Choose Altium Designer
Choose Place Parts
Wait for the Altium Designer to Open (if it's not yet opened)
It will automatically create a Schematic Document where you can place the part
Once it's done downloading, place the part on the Schematic Sheet
Check the Symbol and Footprint is also downloaded.