Hey Michael, welcome to the community!!
There are a couple different threads on the topic on the community that you might find useful.
Also USCCA has some good training available through their services.
https://www.usconcealedcarry.com/product/keeping-your-church-safe/
https://www.usconcealedcarry.com/blog/the-first-step-in-protecting-your-church/
And I’m sure you’ll hear from a lot of posters here with a lot of good advice.
Take it a piece at time. In my opinion, step one is church access and ensuring that there is a window for the congregation to come in, and then the doors are locked/manned (so no one comes in mid-service unobserved). Part of that church access is also having security team members during the entry window welcoming people into the church while also making observations for anything out of the ordinary that may need to be shared/elevated with other security team members.
Second, and something I think is often overlooked, is having a strong trained first responder team with needed tools. I’d suggest 3+ volunteers, one major all purpose first aid kit in a central location and then multiple IFAKs staged throughout the sanctuary so they can be accessed quickly. IFAK should contain (IMO) tourniquet, chest seal, blood stopping agents, Israeli bandage, paramedic shears.
A lot of things will depend on your individual particulars at your church as well. If you have any LEO contacts, you may want to reach out to them for help and suggestions as well.
All that…and we haven’t even gotten to guns yet, lol. Good luck.