Epson Stylus Pro 7500 Reference Manual page 110

5. Hold the ink cartridge with the arrow mark face-up and
pointing to the rear of the printer, then insert the ink cartridge
into the slot until the corresponding Ink Out light turns off.
Note:
There is a protection system against improper cartridge insertion.
If you cannot insert the ink cartridge smoothly, the type of cartridge
may be incorrect. Check the package and production code.
6. Close the ink compartment cover. The printer returns to the
previous status.
5-4
Maintenance and Transportation