This is only relevant if you’re the kind of insomnia that can’t get to sleep but can sleep forever once you are. I’ve suffered for as long as I can remember, even in primary school. It’s affected my life to the point I took work in split shifts to allow me to nap through the day at one stage. This is the only thing to work for me.
The only thing I can suggest is routine. It frustrates me to hear it from people like it’s that easy but the truth is, as an insomniac, you won’t get consistent sleep without a strict routine. You HAVE to get up the same time everyday and go to bed the same time, even if you don’t sleep with the exception of a sleep catch up day at the weekend. You cannot nap. If you start to drop off, stand up, go for a walk... whatever you can do. Trying to be active in the daytime helps generally.
Set realistic times, say 1am-8am. Use prescription sleeping pills to start you off (they’ll generally only even give you about 2 weeks in one go) Then take the strong anti-histamine sleep pills such as Doxylamine succinate as and when you need to stay in it.
You can eventually get the routine but you have to be totally strict.
Break any other habits such as a snack/cuppa or tv show at a certain late time that you can end up staying awake for, no ‘I have to check every social media’ or something that can end up down a rabbit hole, forget any FOMO. The only routine is the getting into bed and getting up.
As you can see I’m not in it right now

being pregnant and unable to take any sleep aids and furloughed so don't
have to get up, I’m finding it impossible.
I had limited success with a sunrise/sunset sleep lamp, more the sunrise element but it may be worth trying. Yoga also helped and grounded breathing.
You have to not pressure yourself, If you give yourself one day, say Saturday for a catch up day, you can survive. Some people only need 5-6 hours, anxiety about not getting enough sleep is a vicious circle. Accept you’ll be tired, accept you won’t be getting 8 hours, don’t overthink or count the hours.

After about 4-6 weeks you should naturally start to feel tired at ‘bed time’.