Please go to My Site → Customize → CSS (or Additional CSS), then add all of the following code to the bottom of that window.
/* This CSS hides the Storefront and Woo footer credit links.
* 11338662-hc (jw)
*/
.site-info span,
.site-info a:nth-child(4) {
display: none;
}
Tip: keep the /*
comment */
in the code to later know what this code does.