You need to remember three keyboard shortcuts to use keyboard macros in emacs.

Type, C-x ( hello C-x ) C-x e C-x e. You will have “hellohellohello”.

Let’s do something more useful like converting a list of words in to a HTML list of links. That is, given two words


convert them into

<li><a href="/contact.html">contact</a></li>
<li><a href="/about.html">about</a></li>

Position the cursor in the first column of ‘contact’ and

C-x ( -- start recording
M-x just-one-space -- remove preceding white-space
C-SPC -- set mark
C-e -- go to end of line
M-w -- yank selected text
C-a -- go the beginning of the line  and type <li><a href="/
C-y -- paste the text and type .html"></a></li>
C-a -- go back to column 0
C-n -- go to next line
C-x ) -- stop recording

To play back the record on subsequent lines, press C-x e as many number of times you want. To execute the macro n times, say 5, press C-u 5 C-x e.