If the components you download from the SnapEDA Plugin are not showing up in your electronic design library,it is possible that the "Library Manager" is not enabled.
Follow the steps below to enable the SnapEDA Library in your Library manager:
Go to your Electronics Design (New PCB or New Schematic)
On the Place Components tab, click on the Open Library Manager button.
On the Library Manager, filter the result by typing SnapEDA and then enable SnapEDA Library.
You should now be able to find the symbols and footprints you downloaded through the SnapEDA plugin.