Navigate to the github page that has each GPG key i.e. they start with:
Then click the "Raw" button on the right hand side. Once the page has loaded, Ctrl + S or File > Save as and save the file. Then import as above, but the filenames should be just "goatpig-signing-key.asc" and "laanwj-releases.asc" unless your browser does something strange or you rename them.