To improve accuracy increase your main ability score at level 4, wield proficient weapons (viewable on character sheet page), prioritize getting +1 magic weapons, and attack from height and from stealth when possible.
As mentioned, if a character's Dex is higher than Str, use missile weapons or weapons with the finesse tag.
The cleric Bless spell and druid Faerie fire both grant extra accuracy. Bear in mind that advantage from the latter doesn't stack with advantage from hiding - they both grant access to the same thing. Devotion paladins have Sacred weapon which boosts accuracy for them alone.
Potions of hill giant strength grant Str21 and are highly prized by any melee fighting type. Buy whenever available!
Spellcasters don't yet have +1 magic wands/staves in EA, so they lag behind in accuracy a bit here.
