Problem with CSS, post padding. (Child thema)

Hi I am new to wordpress and Trying to learn as much as I can, rightnow I have problem with setting margin in my post and few other problem hope you guys can help.

This is my site and I just created child thema, don’t really know much about it, I only have knowledge of html and CSS, I know nothing of PHP and javascrip which I will learn in the future.

I recently created a post and you can see it by clicking on the link , what I want to do is set the margin-right to 100 px so I can have place for google ads, I also wanted to remove the text on top of my site which say leave a reply.

I made an image on my site and colored the part where I want to make change link

Thanks in advance

[Please do not create duplicate threads – your other one was deleted – it does not help you get help faster and creates a confusing mess for volunteers helping out here.]