You can either use the session-wide link, persistent links, or single-use links.

Session-wide link

If it's not practical for you to use a Room, you can distribute the following link to participants.

http://presto-test-server.andrew.cmu.edu/join/nigosisu

Persistent links

For a real session, you should use a room.

Single-use links

Below are single-use links.

P1	http://presto-test-server.andrew.cmu.edu/InitializeParticipant/vkdr2a5s
P2	http://presto-test-server.andrew.cmu.edu/InitializeParticipant/4xcial50
P3	http://presto-test-server.andrew.cmu.edu/InitializeParticipant/keuqoey3