Help required for a simple CSS change that I am not able to manage

any help?

It is always best to include a link to your site when posting a question. That way, not only can we examine what needs to be done, but we can see if you are using a child theme or if you have a CSS plugin installed.

There are a couple of things you can do, depending upon what exactly you want to do. For example, are you trying to hide the page title by shifting the contents up, or do you want the page title to remain visible? If you’re trying to hide the page title, do you want to do so on just the home page or on all pages? Do you want the blue Follow box to be hidden or to remain visible? The simplest thing to do is to reset the value of margin-top for the #page DIV to zero and the value of padding-bottom for the #header DIV to zero:

#page {
   margin-top: 0;
}
#header {
   padding-bottom: 0;
}

This will leave the page title and the blue Follow box visible. If you’re trying to hide the page title as well on just the home page, you can add this rule as well:

.home .page-title {
   display: none;
}

If you aren’t using a child theme, use a CSS plugin like JetPack or Custom CSS Manager.