Page #35 of the manual SERVICE SEARCH
step 1: PRESS MENU
step 2: SCROLL TO SEARCH THEN PRESS THE > ARROW KEY
step 3: SCROLL TO SERVICE SEARCH THEN PRESS THE > ARROW KEY
step 4: SCROLL TO CB AND THEN PRESS THE SEL KEY
You're now scanning all 40 Citizen Band channels.
If you want to program channel 19 in specifically you'll need to follow your manual on programming a frequency into a memory...
Channel 19 is 27.1850 MHz AM