How to make the background of an object transparent?

Question

JPEG

I have a pixel art hero that should be in the game (2D), but:
1) in 64x64 it looks like a mouse when the sprite is placed in the scene.
2) it does not have a transparent background. How to make the character stay and the rest is removed?
first sprite

and here is the second sprite

Answer 1

Remove white background on the sprite itself using Photoshop