Gloomhaven: Jaws of the Lion · Board game rules
Can I use a top action and a bottom action from the same card?
Quick answer
No — you must use the top action from one card and the bottom action from the other card, not both actions from the same card.
Details
On a character's turn, they perform one top action and one bottom action, using their two selected cards for the round. They cannot perform two top actions or two bottom actions [p.7 — Character Turns]. Since a character only selects two cards per round, this means the top action must come from one card and the bottom action must come from the other card — you cannot use both halves of a single card.
The character can decide the order in which these two actions are performed, and can use either card first for either its top or bottom action, but each full action (the entire half of a card) must be performed in the order printed, after which that card is discarded [p.7 — Character Turns].
Watch out: Every card also has small basic action icons (Attack 2 / Move 2) that can replace a card's printed top or bottom action, but this doesn't change the rule — you still need two different cards to supply your top and bottom action for the turn [p.15 — Basic Actions].