You create a sword-shaped plane of force that hovers within range. It lasts for the duration. When the sword appears, you make a melee spell attack against a target of your choice within 5 feet of the sword. On a hit, the target takes 3d10 force damage. Until the spell ends, you can use a bonus action on each of your turns to move the sword up to 20 feet to a spot you can see and repeat this attack against the same target or a different one.
RollQuest ships the D&D 2014 SRD as a content pack, on a 5e character sheet that does the maths - roll from the sheet and let the numbers work themselves out. Free to start.