Custom "Continue Reading" Button

Hoping this is the right place for this, if not, someone please point me in the right direction - I’m completely new to this theme and forum!

On my old Wordpress theme I was able to customize my “Read More/Continue Reading” button using this CSS code:
#page .read-more a {
** background: url(“”) no-repeat;**
** font-size: 0;**
** background-size: 100%;**
** height: 30px;**
** width: 150px;**
** border: 0;**

However, for the Himmelen theme this code doesn’t seem to work and I would really love to continue using my old customized button I made.