Once you get your license you have a 90 day window to use it. I suggest getting the license about 2-3 weeks prior to your wedding day.. It is less chance of losing or damaging it and also gives you time to work through any issues you may be challenged with during the process.
You will need to have at least 1 witness that is 16 years or older attend the ceremony and to sign the license prior to the ceremony as a witness