To put the script into iMacros, hit 'Record', then 'Stop', and then paste the script over the new macro you've created. To run the script every 10 seconds, click the "Max Loop" box and set it to a really high number. (I use 9999999) Then click 'Play Loop', and your Yeah Bot will be unleashed on the world. It should look something like this before you click the button:
Once you've done that, have fun yeah-botting. Enjoy the glorious world that is getting popular for doing absolutely nothing.
Also, if the iMacros window doesn't react to your clicks, move the window around and it'll update the screen. It sucks when that happens, but you can deal with it for a few seconds if it does.
Edit: I forgot to mention that you can change the community by replacing the New Super Luigi U Community link to something else, e.g. the Smash Bros. Community's Play Journal Entries, or Yeah Angel's yeah-list when she gets back to her job.