How do divine and primal spellcasters – that’s to say, Clerics, Druids and all classes that resemble them but aren’t arcane – know their spells? I know Wizards collect them through study and research, Sorcerers through training, Bards through travel and Warlocks… This is answered on page 56 and 58 of the Players Handbook. The only 5e change is a shift away from a specific "call on the deity" prayer to gain (or regain) each spell, as covered therein.

— Ed Greenwood (@TheEdVerse) April 22, 2019