adding new and editing existing content with CMS

Can somebody tell me principle of adding new and editing existing content on the web page?(link to some tutorial etc).

I am currently working on a website project, main page has some news, with photo and text, i added them directly into the code but i think that s not the case, and they should be added and edited by a CMS.

Photos for the news should be properly resized with its aspect ratio and text should be added for every single news.(first news has biggest photo with paragraph and others just small photos with heading pointing to the whole article).

I would just like to hear the principle at the very beginning of my project and to attach it on different webpages which are predicted for changing its content or adding new optionally.