Man has no real equivalent in English. It carries the meaning of one, the general person, but would usually translate into you (singular). Man is a third person pronoun - like han or hun - which means two possesive pronouns: ens or sin/sit/sine (reflexive).
Sin is a 3rd person singular, reflective, possesive pronoun - you are using it when the subject of the sentencence is handeling his or her own stuff:
Man skal lave sit hjemmearbejde. (One ought to do one's (own) homework )
Man skal børste sine tænder hver morgen og aften. (You should brush your (own) teeth morning and evening.)
In all other cases you are using ens:
Hvad gør man, når ens kone ikke vil se finalen? (What do you do when your wife won't watch the cup final?)
Sin may refere to a logical subject which is not mentioned: Det er forbudt at tage sit eget liv. (It' s illegal to commit suicide).
Choose between ens eller sin/sit/sine in the drop down list.