Just copy the output and paste it into your CSS code. For example:
.block {
width: 100px;
height: 100px;
/* dashed border */
background-image: url("data:image/svg+xml,%3csvg width='100%25' height='100%25' xmlns='http://www.w3.org/2000/svg'%3e%3crect width='100%25' height='100%25' fill='none' stroke='%23333' stroke-width='4' stroke-dasharray='6%2c 14' stroke-dashoffset='0' stroke-linecap='square'/%3e%3c/svg%3e");
}
Native CSS properties don't support the customization of border-style. Therefore, we use a trick with an SVG image inside background-image property. The SVG features give us the ability to change the distance between dashed lines, set custom pattern, add dash offset or even change a line cap. Generated SVG image is vector and it fills width and height of elements by 100%, so it doesn't matter what size elements have.