bharara

Hey I get the answer

I am leaving it here so the others can get any help from it

I added this in my style.css of child theme

.site-content .entry-header,
.site-content .entry-content,
.site-content .entry-summary,
.site-content .entry-meta,
.page-content {
    margin: auto 0;
    max-width: 950px;
}

Where I EXACTLY have to place it?

In the head section or at the end of the header

I am using twentyFourteen Theme

I have placed it in the functions.php of my child theme

I am totally new to wordpress and dont know much about PHP

Can anyone please guide me about how to do it

Plus how to make custom menus for eash part like for example, In www.ads-software.com plugin directory, each plugin have a custom menu for its OVERVIEW, REVIEW, FAQ, INSTALLATION etc.

How to do that, please guide me