Hi. First of all, do you really need the snap? Why do I say that, because Biglinux is based on Manjaro / Arch, so by default it doesn’t use Snap packages (which are from Cannonical / Ubunto), but if you really need it, here are the options.
First option: Check out the alternative.to website, which uses google to search for programs similar to the one you’re looking for. It may be that what you’re looking for in snap has an alternative in flatpak, which is a more “accepted” package on all distros.
Second option: Once you’ve overcome the first option, you really need Snapstore, so just go to the Biglinux Bigstore store, in the left-hand bar look for Settings, then Snao Packages, just enable it.
Ps. the Biglinux Store after enabling Snaps will be very, very slow, so I advise you to install what you are going to use and then disable it again.