Take note of the article and section numbers. You will need this information for your citation.
Write "US Const.," at the start of your citation. Do not italicize or underline this. You do not need periods after the "U" and the "S," although you do need one after "Const." to indicate that it is an abbreviation. Include a comma afterward.
Abbreviate "article" as "art." and "section" as "sec." and put the appropriate numbers after each. Separate them by a comma and place a period after the section number.
Add either "Print" or "Web" to the end of your citation. If you have a book copy, write "Print." If you found the document online, write "Web." Your finished citation should resemble this: US Const., art. 2, sec. 2. Web.
Write down the article, section, clause and amendment number as applicable. You will need at least some of this information in your citation.
Write "U.S. Const." Put periods between the "U" and the "S" and after the "Const."
Abbreviate "article" as "art.," "section" as "sec.," "clause" as "cl." and "amendment" as "amend." as applicable. Place the numbers after these abbreviations. When you include an article number or an amendment number, put that number in Roman numerals. Use traditional Arabic numerals for sections and clauses.
Separate the entries by commas. Your final citation could look like: U.S. Const., art. II, sec. 2, cl.1. Or, if you cite an amendment, it may look like: U.S. Const., amend. X, sec. 1.