Remove spare nozzle from acetone bath and gently scrape off any burnt plastic with a ruler or similar. Avoid the nozzle tip if possible.
Power Up Printer, Launch Up Studio application and Intialise printer as per normal startup procedure.
Enter the maintenance menu and click on the 'Withdraw' button. This will heat up the nozzle and the feed stepper will reverse the filament out so it can be removed.
Now click on the 'Extrude' or 'withdraw' buttons to maintain nozzle temp at operating temperature (~260 deg C) you may need to do a few times as it only last for 1 min
Remove nozzle with wrench. Be careful not to burn yourself on the hot metal. Add the dirty nozzle to the acetone bath for soaking.
Screw in the clean nozzle from step 1 - be careful not to cross-thread the nozzle in the hot end and again be careful not to burn yourself on hot metal. Tighten nozzle firmly but do not over tighten.
Reload filament as per normal operation.
In the maintenance menu, click the 'Nozzle Detect' button. This will gently touch the nozzle to the switch at the back of the bed and adjust the nozzle height measurement as appropriate.