I need to know how to get iOS 7 for the iPhone 4 when there's no option to do it in settings?

Jet broke my 5c so I'm using my old 4 I just turned on for the first time in about a year and a half. Extremely outdated and I do not have the option to update it wirelessly and I have no way to get acces to a computer. There's no SIM card In it Would that do anything?

Go to settings and see if you can update it. If it just shows you the ios7 update but doesn't let you install then there isn't enough space to install it. I don't think the SIM card will affect it.