The chrome buttons hide the two tightening bolts in step 8. They are a bugger to put in as they feel they may break as it's not clear where they fit in. I took the photos when replacing a transmission seal on the top case/rear of the 5 speed manual transmission that mimics a driver's side axle leak. The transmission seal that was leaking is the "shift shaft" that bottom shift cable coupler attaches to.

You then need to cut the cable tie as in the instructions. This releases the elastic holding strip and then gaiter from the chrome gear arm. Easy to install ---- Lever Gaiter Ring is easy to install, no need for complex operation, no additional tools or equipment, save time and effort, easy to use I actually took the pictures when dealing with another issue, BUT figured that they'd help out the OP with his issue.I went for the Ivory Leather official gear knob option. It is quite a tight fit to get it on. So a bit of patience you just wiggle the chrome gear arm until the new leather gaiter is on the chrome arm. Then put the chrome surround onto the new gaiter at the bottom. This is pretty easy just unclip from the old one and match to the new one ensuring all clips are in place. You should now have a newly gaitered chrome gear arm with the chrome base attached

High Quality】The shift knob is made of high quality synthetic leather and plastic, comfortable to operate and durable in use. Various unique models to choose from. The shift knob boot is a perfect decoration for your car. OEM standard manufacturing ---- Gaiter Boot Ring complies with OEM standards, replacing OEM number 71775051. Compliance or exceeds the corresponding process standard, and performs strict factory inspection, fully meet the model requiredOriginal size design ---- Lever Gaiter Ring uses the original size design, each material is professional, each process is strictly inspected to ensure the long-term service life of the product Again this feels a bit rough when you're trying to remove it. The gaiter and chrome surround that are fixed to the car are fixed by a number of clips. You can't get to these to release them but they are quite sturdy. I pulled lightly on one side to release the first halt then pulled round the edges. Examples below of both parts.

In the instructions is looks simple, screw driver, lever it off and there you go. In reality I found the gear cap (bit with numbers on) is held on by 4 clip joints to the rubber sleeve attached to it. I spent a good 20 mins trying to patiently remove it in tact. Remember you dont need to replace the original fixing bolt it was only to secure the previous knob. The new knob uses two allen tighten bolts to secure it.If you look carefully at the last 2 pics, you can see where gear oil was leaking out of the transmission seal. I profess not to be an expert, mechanic or Fiat Guru. I like to think I am however quite handy and thought this guide may be of use. There are two clips on each, and the two holes/slots are hidden by the leather cover. They are however near the top of the gear knob when looking at the hole which the chrome button fits into. It’s a case of putting the button in at an angle, clips first, to find them, then when you have located the slots (hidden by leather!) levelling the clip, wiggling and pushing until it clips in.