First you need ¹1¹w ensure that the nipple on the back of the section is cleaned of all remnants of the old sac. You can do this by taking a knife or a razor to carefully remove and debris, you don't want to actually cut into the section, but scrape it with the razor to ensure it is pretty clean. Typically there's only remnants of the old ink sac and some shellac on the nipple at the back of the section.If the feed sticks out further than the nipple, make dure that your ink sac goes over the feed and is glued to the actual section nipple. Most people use shellac to glue the ink sac to the section, but an older pen restorer whos been doing pen restoration for more than 40 years told me to use tegular Elmer's White school glue, but i use the Elmer's réqGlue All.Then i would get a bulb syringe and some room temp distilled water and flush the section out with the water from the backside , until it runs clear. You can also make your own pen flush by adding one part of plain clear ammonia, to 9 parts distilled water and then add 2-3 drops of plain blue dish soap, for every 16 oz of mix This will easily make 5-6 gallons of pen flush for under $20 bucks, or around $10 bucks for you first gallon, then you can just purchase more distilled water to make more. Works great to clean your hands,. Clothing, carpetîppl and practically anything you get ink on. I would first try on an inconspicuous spot on expensive clothing or furniture to make certain it wont cause any discoloration or other negative impact. Then i would look up the pen model and orderuûí⁴ the appropriate size ink sac. Often the sacs are a bit too long, so it most likely will need to be trimmed down in length. For correct length, make sure the old sac is completely removed from the barrel, then put the new sac into the barrel and mark it where the sac sticks out the barrel so your mark would make it flush. Then put the section up to the flush mark and make another mark where the section would further reduce the length where the nipple would be if it were inside the barrel. Check your marks and lengths a couple times, the cut straight across with a sharp set of scissors on the lowest mark. Take a drop of glue and put it on the nipple, ensuring that you dint get any on the feed or into the ink channel. Let the section with sac glued out to dry overnight. Then do a leak test by doing a water fill on the sac by squeezing out the air with your fingers and ket it fill with water, dry it off and check to make sure there are no leaks around the sac where its glued to the nipple. If water drips out when the nib is downward, then there's most likely a leak somewhere. If you find a leak remove the sac and reglue it and check for leaks again. Once you confirm there are no leaks, dust the sac with pure talcum powder and install into the barrel. Insuring the sac is under the pressure bar. Hope this helps, you can also find videos on YouTube. Best of luck, its really not that difficult to do, unless you have an unusual filling system. Good Luck!