Apple i'm a n00b and i don't know what to do

[Empoleom]

i have a used iphone, i downloaded itunes and i upgraded, now it says "no SIM card installed"

 

[vergilite]

well does it have a sim card in it ? check just use like a paper clip on the top to make it open

if there is no sim card you'll have to go fetch one

and make sure its the right carrier for the iphone

 

[jphriendly]

Make sure the sim is seated correctly in the slot (and is free of any debris). I remember reading something about this on another forum...Try going into the settings and turning airplane mode on and then turning it off again. It's not a perm fix, just a workaround.