To create a fomo account, download the app and sign up using your Apple ID or Google Account. That is it. There is no lengthy verification process at signup and no seed phrase to write down.
When you sign up, the app creates a non-custodial wallet that belongs to you. Your wallet is tied to the login you used to create it. If you signed up with Apple ID, that Apple ID is your account. If you signed up with Google, that Google account is your account.
This matters if you ever log out or switch devices. Signing in with a different account than the one you originally used will create a new, separate account. To get back to your original account, sign in with the exact same credential you used the first time.
After signing up, you can connect your X (Twitter) account, set up your profile, and deposit funds to start trading.