Air Carrier pilot reported they confused UN540 and UN545 waypoints on the approach to MMFR airport and descended below the published crossing restriction.

Narrative

I was the PF and we were getting vectored; was then cleared to waypoint UN540 and cleared for approach. I honestly didn't remember if it was clear for the Visual or for ILSDME 4 12R. I mistook UN540 which has a crossing altitude of 2000 feet for the next point; the FAF of UN545 which has a crossing altitude of 1300 feet. I verbalized setting 1300 feet but I must have not said it loud enough as I did not get a confirmation of the altitude from the Captain. As I was approaching UN540 I realized I was at 1300 ft. and was approaching the wrong fix then I initially suspected. I was 700 ft. lower then I was supposed to be. The Captain noticed it at the same time; we were in visual conditions so decided to continue the approach and intercept the GS at the correct spot of UN545. We went on to land without any incident. One cause I believe is I didn't double check the waypoint or I did it to quickly and just saw UN and proceeded to set the wrong altitude. In the future I will double check crossing restrictions more thoroughly and speak louder and make sure I get a response when setting an altitude to allow my coworker to catch a mistake if one made. This was also my first flight back from 3 weeks vacation with an early show. Believe a little fatigue and rust from not being in the plane played a role in my mistake.