Hello
Who can help me with a information?

I want some things.

The post (but only the post itself, not the category or other pages) to be split in 2 columns but by default.
In left column i want the text of the post, and in the right column i want to be the featured image with custom size as: 250x352.

Like in the printscreen I attached.
How i do that?
I use the latest WP and latest ATA.
Thanks in advance

Here are a couple of plugins that may help.
Site Layout Customizer
Drag and Drop Builder Plugin (their themes aren't as flexible as Atahualpa but I like their plugins)

Thanks lmilesw but i think is not what i would like.
I thought you can tell me what file i have to edit to arrange only the post to look like in my printscreen
Thank you

if you want to do it within the theme, you will have to create a template to do it. You can use index.php as a basis and or look at the 'multi column/custom query' template (inclded as of 3.7.7) - you will have to do some custom editing.

I am not that good.
For index - i have a custom homepage.
I thought is like html:
A table:

<table width="500" border="0" cellpadding="0" cellspacing="0">
<tr>
<td width="250" height="94" valign="top">The left column for post with text and body..</td>
<td width="250" valign="top">The featured image with a custom width and height..</td>
</tr>
</table>

I just don't know what is the file to edit only for the post. Not for entire site. I like the categories and hompage.
Can anyone tell me how? or what will be the code to do that?
Thank you so much

It's not a matter of being "that good". That is the way a database driven site works. You would have to build a page template and apply it to the posts you want or use one of those plugins.

If you only want one post formatted a particular way though you could just use the HTML editor in the post and put in a table if you like.