Orihuela Station is on the main line north to Elche Parque and Alicante and south to Orihuela and Murcia.
The line is used by various regional operates, but you can find the timetable using the Renfe website. Click on the word welcome to change the site to English.
For the quicker medium distance trains which just stop at Murcia, Elche and Alicante click on the box which says timetables and prices. The site works using the end stations of each line only, so in this case Murcia and Alicante. In the drop down menus on the Departure select Murcia if you want to go to Elche or Alicante and Alicante if you want to go to Murcia. In the drop down menu for Destination select the end station that you are going to, select the date, then click search. To find the time that the train stops at Orihuela click on the train that you want in the Train/Route column and the time table will pop up.
For the slower local trains which stop at all the stations click on the box which says Commuter Trains (Cercanias in Spanish). Then on the left of the screen click on Murcia/Alicante. In the Departure Point dropdown menu select your departure station, in this case Orihula. In the Destination dropdown menu select the station you are travelling to which will be Murcia, Elche Parque or Alicante. Select the date of travel and then click on search and the timetable will appear. To find the times for the return journey, move your mouse over the words Request Return Times on the Day and once the hand symbol appears click. The Departure Point, Destination and timetable will change to the one for the return journey.