If you are learning to draw have you tried drawing vanishing points yet? If you draw a horizontal line along the middle of a piece of A4 paper you can work out how to do three dimensional objects. Draw a dot somewhere along that line. Use a ruler and draw lines radiating from it. Then draw vertical lines up or down to them. Instant buildings in perspective. You can even use more than one vanishing point. For curved objects like a can or a glass it gives you a clue on how to draw curves and what direction they will be in. Generally upwards if you are looking from below the rim of a can and downwards if from above. It all depends on your eye level. The horizontal line in this exercise represents that. But it’s your choice. The line can be higher or lower (think of the view for a child, closer to the ground, or someone at the top of a bus!)

I used to also have fun drawing boxes with this, or alien buildings, or anything, I tried it with a horse once! You can use soft pencil to draw in the lines so you can erase them later, or use to mark out an object before you start a painting. It helps you sort out all types of things, including portraits or figures. Just play about with it.
I only suggested A4 as that gives you plenty of room…. You can use any size or type of paper.