The 5e D&D Basic Rules v0.1 description of casting times says that spells with a casting time of "bonus action" require a bonus action to cast (p. 79, emphasis mine):
Most spells require a single action to cast, but some spells require a bonus action, a reaction, or much more time to cast.
A spell cast with a bonus action is especially swift. You must use a bonus action on your turn to cast the spell, provided that you haven't already taken a bonus action this turn. You can't cast another spell during the same turn, except for a cantrip with a casting time of 1 action.
It's pretty clear that bonus actions aren't automatic (p. 69):
You can take a bonus action only when a special ability, spell, or other feature of the game states that you can do something as a bonus action. You otherwise don't have a bonus action to take.
So to cast a spell like Healing Word (p. 93), do I
- need to be granted a bonus action that I can use, or do I
- have a bonus action I can use?
I guess I'm unclear on whether I need to have a bonus action before I can spend it on something, or whether having an ability, spell, or whatnot that can be done as a bonus action grants me the bonus action I need to use it.