For every hymn, you can find audio recordings of all four parts both on their own and all together, along with links to the sheet music for you to learn and practice.
The Soprano voice is the highest female voice, and it is normally the melody (the main part).
The Alto voice is for women with lower voices to sing.
The Tenor voice is for men with higher voices.
The Bass voice is for men with lower voices.
Listen and sing along!