How do you make slickers

That will depend on what tools and materials you have access to, how many colors in the image, and what exactly you mean by "Stickers."

Do you want decals for adorning your armor? Then the most common way is using waterslide decals from Hobby Shops or Vinyl decals that are cut using a machine like a Cricut or Silhouette Cameo

Here is how to make waterslide decals at home with no more tools than a home printer:

Or do you mean Stickers in like promotional give away items of a personal logo to give out at cons or put on your armor box as decoration?
In that case I would recommend using a site like Vinyl Disorder or Sticker Mule to get custom stickers and decals made.

Don't want to do that? Then go to an office supply store and get the full page Shipping Labels and print your design on the label paper and cut it out yourself:
Fancy that! I’m working on making a sticker tutorial right now! Won’t be done for a bit… but it’s in the works!

I’m gonna teach people how to make stickers like these bad bois

Your message may be considered spam for the following reasons:

If you wish to reply despite these issues, check the box below before replying.
Be aware that malicious compliance may result in more severe penalties.