Your logo
Open the meeting and go to Branding. Drop in a PNG, JPEG or WebP, up to 10 MB. It appears at the top of the attendee's screen, on the welcome screen, and on the printed sign.
A version with a transparent or white background works best, because the phone screen is dark and the printed sign is white, and one file has to sit on both. A wide logo reads better than a tall one at the size a phone gives it.
Your colour
Frasiey proposes a colour taken from your logo, and you can change it. You pick it as a swatch, not as a code.
Some colours cannot be read on a dark screen, and rather than shipping something an attendee has to squint at, Frasiey says so in plain words: that colour is hard to read on a dark screen, so attendees will see the standard colours instead. Pick a deeper version of the same colour and it will usually pass.
Your welcome screen
This is the first thing a phone shows when somebody scans the sign: a headline, a sentence of your own, the room they are in, and one button that takes them to the captions. It is the place to say "Welcome to the Spring Symposium" and, if it helps, where the coffee is.
Leave it switched off and phones go straight to the captions, which is the right choice for a room where people arrive mid-session.
Check it before you print
The preview on the same page is labelled As attendees see it, and it is the real thing rather than a picture of it. Look at it once on your own phone before you print the signs, because the logo goes on the paper too.
Branding belongs to one meeting. Two meetings can look completely different, and next year's can be set up without touching this year's.
What to do next
When the signs carry your logo, put them up: Print your signs and let people join.