I'm specifically talking about knights in full plate- but I'd be interested in others as well.
Would they have attendants help them? Would they just 'go' in their armor? When in battle could they be able to take the time to do this?
Could you specify by year and region or specific armour? "Plate" is fairly broad, and there's going to be a big difference between, for instance, armour for fighting on horseback, and tournament armour for foot combat.
Depending on specifics, the answer can range from no problem or doable but not pretty to impossible.