I don't know anything about importing sprites into SRB2 projects, but you can use a variety of different tools to make sprites such as paint dot net (The dot is a period in program's actual title, but you should search it by spelling out dot if you want search engines to know you're not looking for a website) and GameMaker. If you don't know much about the actual creation process of sprites, a good starting point I would recommend is practicing by editing old NES Mega Man sprites to look like different characters. They are very simple sprites, and so they work as a good canvas for beginners to work with.
If you're going to use paint dot net to make sprites from scratch, I'd recommend to always remember to turn off antialiasing so that your pixels remain nice and sharp. Regardless of what platform you choose to use however, think about pixel art similarly to how you would think about regular drawing except under the limitations of pixel scaling. The larger of a scale you are working with, the more detail you can give your sprites but the less they will still look like pixel art. The opposite is true for working on smaller scales. I'd advise against outright tracing if you're planning on actually releasing artwork, as that is a form of plagiarism. However, it can be helpful to have a reference image open to help you understand what certain characters/things are supposed to look like.
There's also a bunch of pixel art tutorials on youtube. If you're planning on making an SRB2 character, I'd recommend seeking out some that also go into how to animate pixel art, as obviously you are going to want your character to have more than just idles.