so i wanna start doing pixel arts. but i have 0 idea how to start-- i have both paint tool sai & clip studio;; are these acceptable for pixel art?
what size canvas should i use?

if you have any tips + links to good information, please share!

Find an art program you're comfortable with. For me its MS paint, but you can use any program with a binary pen (should be any of them). Only reason why you would use a program instead of what's built-in is for the layers option.

Take it slow, pixel art takes practice. There are plenty of great tutorials on Deviantart. I'm currently learning from this one to make bottles because I want to open some kind of art shop soon.

Paint tool sai should be good enough.

You should start with warmups. Make small objects like hearts and challenge yourself. For example, you could make a heart in a 3x3 dimension, then go up to 6x6, adding detail and so on. I would also encourage doing bases or sprite edits because that's how I learned to get better. It's easy to do a sprite edit because it challenges you to make it blend into the art.

A good place to start is to look up tutorials.

http://pixeljoint.com/forum/forum_posts.asp?TID=11299 is a very thorough guide. It covers the basics very well, goes over common mistakes, and even gets into more advanced techniques. Even an experienced artist could learn something here.
http://www.yarrninja.com/pixeltutorial/ is another in-depth guide mainly focused on creating assets for video games.
https://www.kawaiihannah.com/pixelart/tutorials/ there are some tutorials here mainly focused on dolling. Great if you mainly want to make characters.
https://lospec.com/pixel-art-tutorials this is a directory of pixel art tutorials. you can find some good stuff here.

There were some other sites I used for tutorials back in the day but they don't seem to be around anymore. :(

And you can always look on google to find more. There are tons out there; you can find something for just about anything you need help with. Also, general art tutorials are also relevant in pixel art. A good foundation in things like composition, color theory, anatomy, etc. is just as relevant in pixel art as any other medium.

You can use just about any graphics software to do pixel art, as long as you restrict what tools you use. No fuzzy brushes, blending, gradients, etc. I started out making pixel art in OHRRPGCE which was this REALLY oldschool DOS-based game maker. Then for the longest time I used Microsoft Paint. The program I use these days is Graphics Gale. It's free (there used to be a paid version but they made it 100% free back in 2017) and it's specifically made for pixel art. Other pixel art specific programs that are popular include Aseprite and Pyxel Edit but I am not really as familiar with those and I don't think they are free.

The size of canvas you use is up to you. It takes longer to make larger things, but it is easier to fit in the details you want. A smaller canvas is simpler, but it can be a challenge to fit everything into a smaller space. It's better to start out making smaller things and work your way up. A lot of the times I'll start making something big and never finish. In general, I'd recommend staying under 300x300 pixels for pixel art, although I've definitely broken that rule plenty of times. Around 32x32 to 100x100 is a pretty fun size to work in; it's quick to make lots of little cute things that size. I tend to make a lot of characters between 100-200 pixels tall. It's a good size to be able to fit in more details without being too big of a project.

Hopefully that helps. If you have any questions I'll do my best to answer. Can't wait to see what you make!

@Tsundererra: I might. These days I start a lot more than I finish. Working full time leaves a lot less time for art.

Learning traditional art can also help you as you'll be learning about shadows and lighting which can help your pixels come to life.

I also recommend tutorials by mortmort on YouTube as they're very good and cover a wide range of things.