Add "included" Channel to Lineup - XFinity

XFinity-Comcast channel programming, Add "included" Channel to Lineup?, I keep finding channels on my screen with the X1, which displays a msg. to the effect of: adding an already "included" channel to my lineup (at no additional cost) by going to & selecting "My Account." It's not nearly that simple! I've spent hours trying to find this function, & the closest I've been able to come is to see my geographic region's channel lineup for any and all channels... nothing about adding a channel to my own tier's lineup! Does anyone know how to do this? Thanks!