casemod lighting help

so im modding out my case and ive never used led lighting. im using a 5v power leed and i need to know what kind of resistor i need for a 3.2v 20ma red led

also i have an older soldering iron. it used to be my dads but ive been using it for a while. i dont know what temp it gets to but its about 15-20 years old. i was wandering if this would be usable or if it would be preferable to buy a cold soldering iron. i used to have one but my appartment got robbed a year ago and i lost almost everything

Is this any help ?

i actually came accross this and this after posting. they did what i wanted to. alot of awesome info on the first link to. your info would have helped but not quite as well. since alot of digging was needed