Add a background image to header

@sanket: Go to Dashboard=> Appearance=> Customize=> Theme Options=> Custom CSS box and add the following CSS:

header#branding {
    background-image: url("http://www.myblog.medtreatserve.com/wp-content/uploads/2016/03/linkedinbg4.jpg");
    background-position: center center;
    background-size: cover;
    background-repeat: no-repeat;
}

Note: The image you are using for the background seems quite small, I recommend you to use a large (not too large either) one instead.

Let me know if any problem.

Regards,
Mahesh

@sanket:
1. Change the text color below the Featured Post Slider:
Go to Dashboard=> Appearance=> Customize=> Theme Options=> Custom CSS box and add the following CSS:

#main-slider .featured-text {
    color: #ffffff;
}

2. Change the hover color of Header Text:
Go to Dashboard=> Appearance=> Customize=> Theme Options=> Custom CSS box and add the following CSS:

#site-title a:hover {
    color: #ffffff;
}

3. Want to customize the footer to my name where it says Powered by WordPress | Theme Simple Catch Pro:
Go to Dashboard=> Appearance=> Customize=> Theme Options=> Footer Options and in Footer Editor options, replace the following text there:
Powered by: [wp-link] | Theme: [theme-link] with
your name

Let me know if any problem.

Regards,
Mahesh