Center Portfolio Items in Zerif Pro

In case you don't have a CSS plugin, we advise you install    Advanced CSS Editor plugin and follow the instructions. In Appearance -> Customize -> Advanced CSS Editor add the following code.

If you are using WordPress 4.7 or later you could add the code to Appearance->Customize->Additional CSS.

.cbp-rfgrid li {
    margin: 0 auto;
    float: none;
    display: inline-block;