I don't know how to create a drawing

How in the world do you create a drawing of your own?

Have you used any kind of digital drawing/painting or image manipulation application before? If not, you’re in for a long and steep learning curve.

However, the good news is that it’s not all that difficult. (Making good looking pictures is difficult but that’s a different subject.)

Do you have a drawing tablet or will you be limited to using a mouse?
It is possible to paint/draw with a mouse but it’s not a very comfortable experience compared to a drawing tablet.

Here is the manual which is very well written and covers lots of things:

You Tube has many video tutorials for krita, including those that tell you how to download it and install it and set it up in various ways, so I suggest that you watch a few of those to get an idea how to use it.

If none of that helps, and do give those learning resources a try first, get back to here and say what stage you’re at, what you see on the screen and what seems to be puzzzling you.

Actually it is too undefined broad question.

If you talking how to draw and paint you need video courses, lessons, tutorials or books.
If you talking how to draw digitally you need tablet and to check some manuals about software you going to use.

Is it possible to draw on a cromebook

Chromebooks use Android. I could recommend “Infinite Painter” and “Artflow” apps. Chromebooks also support Linux apps, so it possible use Krita, but you need how-to tutors (e.g. https://www.youtube.com/watch?v=9R-_E5Ui15k ) Secondary, you need a tablet that supports Android (watch some YouTube reviews) . I know some of Huion and XP-pen does it. Also Wacom Intuos (CTL4100 and CTL 6100 models) supports Android. And you need to check a problems/questions that users have with tablets.