Congrats on getting into winemaking, you will really enjoy it.
The hydrometer is your friend. Even if the kit instructions state to do something after a certain amount of time, your batch will vary every time based on things like temperature, freshness of ingredients, etc. So it may progress slower or faster than the instructions. The hydrometer will also let you know if the wine is progressing at all - it will save you from racking or bottling a wine that hasn't fermented entirely, and also let you know if fermentation is stuck. As long as it is cleaned and sanitized, then it will not contaminate your wine. You would benefit from a wine notebook or journal where you can make notes with dates of starting SG (specific gravity), SG at each stage, and final SG.
K-meta is important to be used to stabilize after fermentation is complete. Next batch, take a hydrometer reading to be sure that has happened, then add the k-meta. Dosing is on the bottle; if your kit contains a package of it, put it in per the kit instructions.
Sorbate is important when you'll be back-sweetening the wine. Add along with k-meta at stabilizing time. Dosing is on the bottle; if your kit contains a package of it, put it in per the kit instructions.
Can't give any advice on the wine conditioner you're using as I have not tried that one.
The suggestion above to taste the wine before adding anything is a really good one. The reason is that you may not have fermented to "dry" so your wine may already be sweet.
Feel free to ask questions, there are folks in this forum who have made hundreds or thousands of batches. Also consider getting a book about winemaking fundamentals... it's helpful to know what's happening and why.
Good luck!
Heather
