Sign in with the Gmail or a Google Account email used for the account.
Go to the Users page and click the pencil icon. If changing the user's role from mobile to web/mobile, enter a Gmail or a Google Account email in which they will sign into the website with.
Sign in with the Gmail or a Google Account email used for the account.
Go to the Users page and click the garbage can icon. Note that you cannot delete a user with data that has previously synced to the cloud and there must always be at least one web user.