A couple questions

I am going to be using newspapers for substrate since I have a whole bunch of it already. My question is, will this be okay and how will I keep the humidity up if I am using newspaper ?

The enclosure I am using is a sterilite container.

Newspaper is great. Humidity is much easier to control when you use a tub. Heat lamps are what makes keeping humidity levels impossible (as well as screen tops) if your humidity is low you will just have to mist the tub (it's fine to get the paper wet)

To keep humidity all I do is mist? I don't need to add like a wet towel or anything or maybe a little bit of moss in there to hold the moisture?

You can do all of those things but before you go to such measures give misting a shot. I know that I live in a tropical rain forest compared to most of the people on this site (Florida), but as soon as I stopped using glass tanks and heat lamps I have had 0 humidity problems. My cages stay around 50% normally and if I must them I can get them up to 80% and it will stay that high for a few days. A tub with a UTH should be the same. Without a heat lamp to suck the moisture out of the air and alid to help hold it in humidity is super easy.

If you do have problems, then you might have to take more drastic steps like the ones you already mentioned but for not i'd say just wait and we what you are dealing with.

I have mine in a rack and with the large water bowls and bedding I had to add some extra ventilation because my humidity was too high (and its at about 25% out of the tubs). Get it set up and running to see where your levels are at and then go from there. You may not need to do anything or you may just need to mist. Good luck:)