Hi Cristie, and welcome, I hope when you feel comfortable you will come and post any questions about Lantus over in the subforum.
https://felinediabetes.com/FDMB/forums/lantus-basaglar-glargine-and-levemir-detemir.9/
I see further above in your post that you were asking about when to test, feed and shoot?
To answer that question, we recommend that you test, feed and give insulin all within 15 minutes or so. You want to test first, to make sure it is safe to give insulin.
In general, it is suggested to withhold food 2 hours before preshot so as not to have a possible food influenced number when you do give insulin. That can artificially inflate the BG which is particularly problematic if the test is a lower number. You have no way of knowing whether that number was bumped up because of the food that was eaten. Of course once you get a better idea of how your cat responds to insulin and carbs in the food, then this can potentially be relaxed. There is a lot of information to absorb, so we will be happy to help you if you have any questions.