Epson LQ-800 User Manual page 121

Removing
Figure D-2. the ribbon cables
Installing the new print head
Connect the ribbon cables to the black connector blocks by gently
pushing the ends of the cables into the blocks. Place the new print
head on the carriage, making sure the guide holes on the print head fit
over the guide pins on the carriage.
Snap the black locking levers back in place, and that's it.
D-10