XF 1.5 Change Default style to fit own HTML node as tab

#1
need your help with coding. I want to add my own HTML code to the newly added node as tab.
I have basically added the HTML code but it does not automatically fit within the default template.
As I understand, I need to amend page_node.css? Am I right? If not, what should I do?

Thanks!
Belka
 
#3
Thanks for a guide, I did put the HTML code into template's HTML code box, however it doesn't display as should.
Text position is not within xenforo borders, no figures displayed, etc...
 
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