How to set font style light?

I m making a web site from photoshop sketch. And I have a text wit

font-family Segoe Ui and font-style: Light. In photoshop It looks like this:

So how to set this in css to p element?

p {

}

Use font-weight which takes values like:

p {
    font-weight: 100; /* 100, 200, 300, ... 900, normal, bold, bolder, lighter */
}

See the documentation on W3Schools.