If you are having problems figuring it out, take a look at the AR Paragraph 1. I just scroll down into the example memorandum that I am looking for and just copy the formatting.
If you would like to download an editable memo example click here. This is the subject line. Enter your full name in all capital letters. Heading: This is the header of all memorandums.
If not, find an old memorandum that was used by your unit before and it should be there. Write in an informal tone with one- and two-syllable words. It should be exactly the same as the ones you used at the beginning of your memo. The Army sets high standards and provides specific guidelines for non-ambiguous, clear writing in Army Regulation"Preparing and Managing Correspondence.