I assume this is for 2D?
Are you using a built-in control?
Generally, that'd work similar to the animation setup explained in the 2D quickstart tutorials, but instead of using 4 directions you'd just use 2 (e.g. 0-1 for one direction, 2-3 for the other).
Or, just have animations for one direction and flip the sprite (negative scale on the axis). The built-in Top Down 2D player controls have an option to flip horizontally or vertically.