On some cartridges you have to drill a hole for the needle or force out a little plug. The little rubber bungs are to plug that hole.
Refilling 'frames' are dedicated to each type of cartridge and seal around the jet part, you can suck the air from under the seal with a syringe and so start the ink flowing.
As it has been dry for a while the tiny jets may be blocked, if soaking them in solvent does not work, you will probably need a new cart this time.
Plenty of refills in a single kit tho'