How do I take measurements for shorts?

Yes! Some players wear shorts while playing softball. Just be careful about how you slide—you might want some extra coverage, like a slider on your knee.

You're going to need to increase the width of the leg and then either gather the leg openings or run elastic through them.

You can with an elasticated fabric. Take your measurements as usual, and make sure that you do not make the leg cut so high that they seem like briefs/knickers. Use...

For most of them it tells you the measurements right beside the components.

Use your tape measure to measure around your waist, about 2" above your belly button. Take that measurement and multiply it by 1.5, and write that number down. Then, measure...

Get measurements for the neck, chest, sleeve, waist, and hip. Also, measure from the front left edge of the neck to about 3 in (7.6 cm) below the waist band.

On the image, it says 0.25 inches, which would be 0.63 centimeters. A quarter of an inch is also 0.63 centimeters.

The metric system is most commonly used worldwide; the USA still uses inches, feet, yards. You can convert to inches, though, if inches/feet /yards feels more comfortable to you.

Yes, they'll just be mid-rise shorts. I actually prefer to cut my mid-rise to high-rise jeans into shorts since they make for a more flattering style.