Firstly, you do want to protect yourself. A simple necklace you've employed to protect your sleeping body is perfectly fine, nothing fancy.
Also try to have a comfy spot for this (not too comfy! You may fall asleep, which is OK and common, but can be frustrating).
There's a few methods, but I'll share the one that personally works for me.
Do a body awareness scan (just a form of meditation where you lay down and relax, paying attention to each party of the body, relaxing all your muscles from the tops of your toes to your forehead). Imagine waves of calm going up your body, becoming looser and more relaxed (yet aware).
When you almost begin to feel numb, sometimes a buzzing sensation, lift your arms and legs a few times. Pay attention to how that feels, what muscles you're using. Relax again, taking the time to become loose and calm.
Now, focusing on how you are present in your body, become aware of what it's like to take up the space of you body, as if you're inside yourself. Try lifting this metaphysical arm, this "idea" of your arm- don't lift your actual arm. Flex and move your astral form. You essentially end up using your arms to push out of your body. It can take a few tries.
There are other methods, as I mentioned, such as the rope method. Searching "astral projection rope technique / method" works perfectly fine, just comb through multiple different sites and use some common sense.
I am absolutely not an expert and I'm speaking from my own personal experience. If you want more in-depth research that's been vetted a bit, try the Archives server on discord. It's just an archive of witchcraft and folk-related books and resources. They have some stuff on astral projection. Here is the link:
https://discord.gg/ssYZDp2x
Posting that publicly if other people want to use it.
Wishing you tons of luck, and don't beat yourself up if you have trouble!