Hello @SMH_ZSL24, and welcome to the forum!
You can use it and there is even a press-kit with resources, like Krita’s logo, you can download and use. It is also no problem to show Krita’s interface, if in full or in part, does not matter. But you won’t get a written permission for it, because no one got one so far, but I’ll give you links to Krita’s official pages that are enough to check for anyone who is not sure about this, that it is allowed in the borders described there:
Can I use Krita commercially? →
Krita’s press kit with resources you can use to present your screenshots or videos with Krita can be downloaded from this address:
Michelist