Stabilizing your wine, cider or mead is a process that prevents fermentation from restarting and protects your wine from any forms micro organisms or oxygen that managed to get in while racking. These unwanted additions can cause spoilage, cloudiness or oxidation.

Stabilizing is usually done just before bottling, especially if you want to back sweeten your wine (adding more sugar after fermentation to make it sweeter)

There are a couple of ways people choose to stabilize. The most often used, and most practical way is after your wine is completely finished fermenting, and has cleared or dropped out and is ready to be bottled..add potassium metabisulfite (campden) and potassium sorbate. These chemicals work together to kill off any yeast and bacteria that could cause re-fermentation that spoilage.

Your best bet is to read the dosing amounts on your packaging, but the long standing dosage amounts are 1/2 teaspoon of the Potassium Sorbate and 1 crushed campden tablet per gallon used prior to final packaging.

Just mix your measured amount of each in a small bit of water, then combine with your wine. Be sure to wait the standard 24 hours to let it off gas the sulfur before sweetening or otherwise packaging.

There are those who pasteurize, or use heat to kill off any microbes or yeast,, but this can lead to off flavors, protein haze and even oxidation if too much heat is used or for too long.
I for one use the Sorbate and Campden method.

There you go. Stabilizing your wine is an absolute must of you plan on back sweetening. And even if you are not, it’s easy insurance against a lot of post fermentation problems.

Sources https://winemakersacademy.com/stabilizing-wine/
https://en.wikipedia.org/wiki/Clarification_and_stabilization_of_wine
https://celebrationgeneration.com/how-to-stabilize-and-back-sweeten-wine/