You’re like me … I prefer the minimalist look so have already got this configured.
You can hide them with custom CSS, on the web, click on the Gear, Account, Custom CSS/Javascript and add:
/* Hide Add + Discover Sites */
.NB-feeds-header-container.NB-feeds-header-river-container.NB-feeds-header-add-site-container {
display: none !important;
}/* Widely Read Stories */
.NB-feeds-header-container.NB-feeds-header-river-container.NB-feeds-header-river-well-read-container.NB-sticky-sidebar-section {
display: none !important;
}/* Hide Long Reads */
.NB-feeds-header-container.NB-feeds-header-river-container.NB-feeds-header-river-long-reads-container.NB-sticky-sidebar-section {
display: none !important;
}