Rounded Corner Borders

[BeautyHealth.com.cy]

I am trying to add rounded corner borders. It is very easy and have used it before in another site.

The problem is that i cannot figure out where in my stylesheet i should add the rounded corner border code.

 .pmb1_b, .pmb1_s {font-size:1px; }
    .pmb1_1, .pmb1_2, .pmb1_3, .pmb1_4, .pmb1_b, .pmb1_s {display:block; overflow:hidden;}
    .pmb1_1, .pmb1_2, .pmb1_3, .pmb1_s {height:1px;}
    .pmb1_2, .pmb1_3, .pmb1_4 {border-style: solid; border-width: 0 1px; }
    .pmb1_1 {margin:0 5px; }
    .pmb1_2 {margin:0 3px; border-width:0 2px;}
    .pmb1_3 {margin:0 2px;}
    .pmb1_4 {height:2px; margin:0 1px;}
    .pmb1_c {display:block; border-style: solid ; border-width: 0 1px;} 

I have added it in my template stylesheet but it does not work.

Is there any certain place to add my code or just drop it somewhere in the stylesheet?

Im using cherry_zen template.