As of right now, the cmdline can be brought up by pressing :
and this window can be closed by pressing q+RETURN

What is this?

ssm is a simple stream manager inspired by multitwitch, dwm, and vi

Available commands are

youtube VIDEOID open youtube live stream with VIDEOID
twitch CHANNEL  open twitch live stream at CHANNEL
help            open this help box
quit            close currently selected stream

you may find...things, by looking at the source for this page

Available keybindings are

j/k   cycle through open streams
q     opens cmdline to close selected stream (you just need to press enter)
SPACE set selected stream as master