welcome to the forum
@Dave Bee .
The pink Puss is succinct, but exactly right. And follow the manufacturers label.
Treat now.
In spring- use the other product.
Apart from being a beginner, and I'm guessing you bought a hive or nuc in Sept, you don't give much information about the hive, or your beekeeping. The best option in this case is to treat your hive using a mainstream product, following the recommended doses. When you have a winter or two under your belt- you may look to alternatives.
Spend some time reading the green book by Mark Goodwin & Michelle Taylor- Control of Varroa. I think it may even be in the forum resources.
You may have left it too long, but then again, it might be just the right time to be treating. Learn how to assess your hive for varroa load and remove any guesswork.