The default location for the secondary menu in the DIVI theme is at the top of the screen.

To make it to be below the Primary menu - between the header and body of the page, add the following in the custom CSS menu.

@media only screen and (min-width: 981px) {
#main-header {
top: 0 !important;
#top-header {
top: 134px !important;
} }