Leaving my opinion about needing an Ubuntu account aside, you should do what the error says: provide the snap command.
My guess is the Snappy store is missing, so you will have to install it manually. Open up a terminal, or, if you can't because of not being logged in, you can use [CTRL] + [ALT] + [F2] in order to get to a terminal input. Ideally, you should be able to login as a local user. From there, just use apt to install snapd and you should be good to go. If you had to use the function keys to open a terminal, iirc, the DE should be on [CTRL] + [ALT] + [F7] by default, but you may test all function keys until you find it.