There are several ways to make stickers.
Use preformatted purchased Labels. These come in all sorts of shapes, sizes, and paper type. Avery is the most common brand. These can be purchased online or any office supply store. It's basically printing on a mailing label.
Print an image on a full sheet of sticky back paper using an inkjet or laser color printer, then custom cut around each image with a vinyl cutter using CutStudio software. Print and scan registration marks.
Use simple Cutstudio software to generate a sticker using it's design tools, text, or import and trace feature.