The answer of Lennart is wrong. You can not swich of security in the cloud. You can only do that locally. You need to enable anonymous users: https://docs.mendix.com/refguide/anonymous-users#1-introduction
Or you could enable demo users: https://docs.mendix.com/refguide/demo-users#1-introduction But do note that anybody could then log in as that demo user.
Regards,
Ronald