Help making images on my homepage smaller for the phone/tablet view only.

Site URL: http://www.alinapatra.com

Hello there!

I am trying to make my photos for the mobile version smaller on my homepage. The photos are extremely zoomed in and it would look so much better if I can fix this.

I have a code already entered to change my social media icon colors and it worked like a charm. Then I pasted another code below it -- in attempts to fix the problem -- but it keeps saying there's an error on one of the lines. 

I am not a code person at all. This is like a foreign language to me so any help would be appreciated. Here is the code I copied. 

/* CSS FOR TABLET AND MOBILE */

@mobile: ~"only screen and (max-width: 640px)";

@tablet: ~"only screen and (min-width: 641px) and (max-width: 949px)";

/* CSS FOR TABLET */

@media @tablet {

/* Insert Code for Tablet Below This Line*/

/* Insert Code for Tablet Above This Line */

}

/* CSS FOR MOBILE */

@media @mobile {

/* Insert Code for Mobile Below This Line*/

/* Insert Code for Mobile Above This Line */

}

Thank you so much!!!