How can you easily insert a tampon?

Firstly make sure that you're using the correct absorbency for your flow, always use lowest absorbency and ideally use during full flow, also try cotton tampons which aren't as rough as rayon tampons - another option is soft or sponge tampons which are squishy and moistened before use.

Try to masturbate before insertion, when aroused the vagina relaxes, lubricates, opens, and increases in size (to avoid pain or damage during sex) so it can make tampon insertion easier. You can also use lubrication on the tampons like KY Jelly or olive oil to make insertion easier too.