First water change question

[johnsamm7]

So I'm about due for my first water change this is my first time doing it just made 5 gal of r/0 water planing on Mixing the salt is there any specific time I have to mix the salt for 48hr minimum or something I have to do and heat it to the same temp. I've read different percentages to do ranging from 10-25% which one should I do and how long do I let the salt mix for

 

[Tahoe61]

Follow the directions on the salt mix container and you can not really go wrong.

If I am in a hurry I mix it for roughly an hour or two (I/O salt) with a power head.
If I am not in a hurry I mix it the day before.

You do not want to see any salt crystals still undissolved within the solution.