How do you do that? Resizing the window?

If I have to resize the window then it will resize other tabs. If I need to put this in a different tab then it is kind of a hassle for a site that does not look that welcoming to me.

Probably there are some middle ground here.

I just resize the window when I start reading. And when I close the tab to read something else I resize the window again to fit that content. Now when I've made aware of it, I realise I do it all the time without thinking.