If you take a look on line 1318 in your css you can adjust the padding top and bottom –
.welcome-wide .wrap {
margin: 0 auto;
overflow: hidden;
padding: 60px 0 30px;
width: 1140px;
}
You can adjust the padding depending on how much smaller you want it to be – padding: 60px 0 30px;
In this case, the top is 60px, the 0 is both left and right, and the 30px is the bottom. If you increase or decrease the top, just make sure you add the same amount to the bottom. Example, if you decrease the padding-top by 10 or 20px, then you’ll need to do the same for the bottom since they are equal in this situation.