Smiting Question

[Pichu]

If I wanted, could I, as a Paladin, use my bonus action to cast a smite spell and then, when I attack, use divine smite? TIA!

[Plaguescarred]

Yes of course! As long as you have enought spell slot you could do this. Divine Smite doesn't use any action.

[Arkhios]

If I wanted, could I, as a Paladin, use my bonus action to cast a smite spell and then, when I attack, use divine smite? TIA!
Yes of course!

Affirmative.
Although, you don't decide to use a divine smite when you attack, instead when you hit.

[Plaguescarred]

Even better on a nat 20!

[DivisibleByZero]

Just remember that the smite spells don't exist for their damaging ability, they exist for their riders. Use them sparingly unless you're really trying to nova.

[Yuki Akuma]

Important reminders:

Smite spells last for one minute, so even if they miss you can try again.

Smite spells are Concentration spells, so any other Concentration buffs you have on will turn off immediately when you cast a Smite spell, even if you hit with it in the same round. Also, if you miss and retain the spell, you need to make a Constitution save every time you take damage.