I'm going to give a bit of the overall picture so you have some idea of the direction you need to go.
The basic theme with Lantus is, "Shoot low to stay low." For those of us who are experienced with Lantus and have accumulated a fair amount of data on how Lantus effects our cat, we will typically shoot any pre-shot number larger than 50. I'm sure that sounds terrifying! Be assured, none of us wake up and feel comfortable a few weeks into our cat's diabetes journey shooting that low. What I encourage caregivers to do is to mentally decide what the lowest number is you feel comfortable shooting. With TR, the "post and ask for help" number is 150. So, you could, if you feel comfortable, shoot any number above 150 and ask for input if you get a number below 150. If you've shot around 150, then what would the next lowest number be that you would feel comfortable shooting? You work your way down to shooting low numbers.
All of that said, you must have supplies on hand to shoot low. Make sure you have a stock of strips and HC food if needed and that you can be around to monitor.