Onkyo HT-R550 old receiver, new use (1 Viewer)

[perplexednovice]

Trying to use an old Onkyo HT-R550 for a dance studio that will need audio input from a 2.5 jack of a computer and/or ipad/iphone. I am looking for the best option to use and the best ports to hook the cord into. I see 2.5 to component cords online, wondering if that is the best option (or a 2.5 to optical considering the backside of this equipment?), and which ports on the back to plug into (just the CD in the case of components? I would really appreciate any help you could provide, thank you. https://www.manualslib.com/manual/115340/Onkyo-Ht-R550.html