Okay so making todo lists is only a sub-section of tagging. Tagging is how Thinkery allows you to categorized all you thoughts into easily defined groups. It is the same process as when you were making the todo lists:
1) To tag a thought just place a simple hashtag with the thought.
eg: Remember to buy bugspray #DEATHTOALLBUGS
Paint the patio #onemorereasonshe'snotgettingachristmaspresent