images on wellcome page and post pages

[twistin]

Hello;
I am trying to implement a blog in which I would like to be able to write music, education and technology content. I have seen your theme Gatsby theme minimal blog and I liked it very much for its simplicity.
I already have it installed and I modified some things like title, presentation, post, etc...
Now I have some doubts-problems because I am not aware of React-Gatsby- etc... that is to say I am an absolute beginner.
Could you please explain me in a simple way (if possible) how to put in the post images and/or videos that accompany the text.
I would also like to know if on the home page every time a new post is published it can be accompanied by an image.
Thank you very much and excuse my ignorance.
Regards