Make sure you have read the legal bit on my home page.
The verb tense for first-person wants is pre-masu stem + taidesu. It works as an i adjective.
tabetaidesu. "I want to eat."
odoritakunaka,tadesu. "I did not want to dance."
Note that it is very easy to confuse this verb tense with itaidesu, which (as seen here) means a pain.
atamagaitaidesu. "My head aches." The alternative parsing, "I want my head to be present", is rather unlikely (but not grammatically incorrect).