Ii is compono, componere, composui, compositum - it means "to compose (poetry)" - active voice, "to be buried" - passive voice. The form from the text is passive voice, infinitive, present.
This "sic ego componi velim " could be translated "In this way I wish to be buried". I must think a little to the last part because it is not very logic for me and I'll be back with the translation.