How can I get the black ink into the tube/line on the right? HP 3520

I’ve tried all the many suggested ways to clean/maintain/align, disassemble and soak the print head, etc. What I think is the problem is the clear tube(s) on the right are mostly empty. I think there may be a clog in the line. I cleaned tons of gunky ink from the inside bottom of the printer and all around the print head carriage and where it is parked when not in use. How do I get the ink back into the line? Is the sponge on the right supposed to be full of ink?