Thanks for writing in!
On behalf of my colleague, I'll answer the questions for you.
1) I am very curious how I can style my posts as well with headers, background-images, and forms etc. html & css. Where do I place the css and html? I'm not sure where to place it correctly.
You can add a class/ID in the Customize tab of your section/row.
Then you can use those classes/ID's by adding styles either from X/Pro > Theme Options > CSS or Element CSS. I've shared resources to look at.
2) My post are very basic and boring. here is an ex. http://www.selacowdb.com/mock-interview-day How do I change the style the layout to an example like this https://essential.themepunch.com/just-food/doing-it-the-chilled-way/
In the example link, you wanted to have a sticky header, and a full width template posts.
For the sticky header:
You need to make your header bar white, you will also set the position to absolute so it stays over the slider. Don't forget to set it to sticky.
Here's an intro guide to refer about Pro's header and footer builder:
For the full width template:
Go to Pro > Theme Options > Layout and Design and select Fullwidth as layout.
If you need each of your pages to have full width, you can change it in Page > Page Attributes.
2) Please advise I'm still learning I am using xtheme pro 2.0.4. Also how come none of the plugins i install never look like the demo? Even after I enter my own data. How do I get them to look like the demo?
Pro themes doesn't cater X demo templates. I suggest you use the template manager as it has pre-defined design assets such as Design Cloud.
However, if you insists of using X theme demos, first, you may need to activate X theme. Please see tutorial below on how to setup demo content:
Once done, re-activate the Pro theme. Hope that helps you get started.
I advise you create a separate thread next time to avoid confusion on replies.