Using The Tools (Move, Marcquee, Color Picker & Brush)

Move Tool:

Used to move objects around.

Rectangular Marcquee Tool:

Used to select portions of the screen for editing.

Color Picker:

Used to simply select a color for use in editing.

Brush Tool:

Used to brush a particular color into an image.

1)
Open an image (like this one) into Photoshop.

Note: If you didn't copy/paste, but rather file/opened, you will need to double-click the 'Background' layer and then choose OK to the prompt to effectively remove the background layer (notice it change to 'Layer 0').

2)
Ensure the layer with the image is selected, and choose the 'Move Tool'.

3)
Use the tool by clicking and dragging the image across the screen. The image will move and reveal what's behind it (transparent pixels if you have no background and white if you do).

1)
With the above tutorial still intact in Photoshop, move the image back to it's original location (or just start over) and choose the 'Rectangular Marcquee Tool'.

2)
Select a portion of the image desired for deletion by clicking and dragging the tool around that particular section like the bottom of this one:

3)
Click 'delete' to remove that portion.

4)
Navigate to Edit > Step Backward and choose it as many times as needed to undo that edit.

Select the Marcquee Tool again, choose to select the area at the bottom, and click the top double white boxes on the bottom of the tools menu to bring up the 'Color Picker'.

6)
Choose black and then press the letter 'B' on your keyboard to bring up the 'Brush Tool'. Your mouse will change to a circle. You can now brush in the area you've selected to make it black like this:

Choosing to select the area before brushing was merely to contain the brush strokes within the selection. It doesn't always have to be like that.