Need help with latin? My advice is: pick a short phrase (ex: an Introit antiphon) and translate it word by word. How? There’s an app for that : S.P.Q.R. (click on link)
Also, to sight-read and sing Gregorian Notation: app called iChant (for Android)
If you know nothing about chant and want to learn, this is a great app to help you get started.