He just drags the margin and tab icons where he wants them, or he can click in the ruler to set a new tab stop.
He can choose the type of tab stop to set by right-clicking in the ruler bar. If he doesn't see the ruler bar, he needs to make sure that the document is Rich Text, then to to Format -> Text -> Show Ruler.
First make sure your document is an RTF (rich text) document. This is the default format, but can be done in the Format menu where you will have an option to "Make Plain Text" or "Make Rich Text" (if the option here says "Make plain text" then you are already in RTF format and are good to go).
Next press Command-R to toggle the ruler, where you can drag the little triangles to set tab locations.
For margins, you can drag the small downward-facing arrows on this toolbar to the desired location, but there are not vertical margin options in TextEdit.
If you want more formatting options, then you will need a more advanced editor. Some popular ones are of course Microsoft Word and Apple's Pages, but there is the free OpenOffice (or NeoOffice, or Libreoffice) in addition to Bean and Mellel.