Epson EPL-6200 Reference Manual page 309

6. Lifting the Duplex Unit with both hands, carefully insert the
tabs at the bottom of the unit into their corresponding cavities
on the back of the 500-Sheet Lower Paper Cassette Unit.
7. Carefully push the unit against the printer, making sure that
the hook on the top-right corner is firmly inserted into the hole
on the printer.
292
Installing and Removing Options (EPL-6200 only)