If the cell phone is not locked with a different network you can use the MTS sim with your iPhone 5. If not, you should unlock it. I suggest you can approach http://www.mobileunlocksolutions.com/unlock-phone/apple/iphone-5s/ and specify the country,locked network of phone.Based on the availability you can get the permanent unlock service along with free instructions.

Can I use my MTS cDNA sim in iPhone 6 in India?

Can i insert mts sim card in an apple 5s??

Yes, as long as your Apple iPhone 5 is unlocked, then there shouldn't be any problem.