is currently impossible through official Apple channels. Apple stopped signing iOS 13.7 on , shortly after the release of iOS 14.
If your iPhone SE is already on a newer version (like iOS 14 or 15), you cannot revert to iOS 13.7. Download iOS 13.7 for iPhone SE
Apple routinely "stops signing" older operating systems to ensure users remain on the most secure and up-to-date versions. is currently impossible through official Apple channels