a basic necessity in a pixel art tool is Brush and Eraser Tool, CSprite Provides Some Variants Of It, A Square, Circle Brush & Eraser.
You can Select The The Brush Tool by pressing the B Key on your keyboard, Whereas for Eraser you can press B Key.
If you hold down the Shift key and then press the B Or E Key, you can select the Square Version of Brush/Eraser.