I have two good friends that I want to marry so they can get their citizenship.
How do I do so?

Getting married does not get them any citizenship at all.

To marry you get a marriage license like anyone dles

If you are only marrying to provide an immigration benefit and not to have a shared life together as husband and wife, it is illegal.

The USCIS officers are well-trained on sham marriages and both of you will be caught at the 245 interview. The beneficiary will be deported, barred and you may be fined.

Don't do it.

I have two good friends that I want to marry so they can get their citizenship.
How do I do so?

You can't marry TWO people. It is against the law and called bigamy.

Did you say TWO GOOD FRIENDS? What kind of idiot are you to think of doing such a thing not only once... but twice? I think you should pick your good FRIEND'S country and go back there together :/ BLAAHHHHH! Tell your 2 good friends to find sponsoring companies to help them to get work visas, and keep yourself out of the marriage for citizenship business. That is just amazing to me, that people would be so ignorant... sad.