People think angels are exclusively Christian. They are not. You’ll even find angels in Islam and Judiasm. Some pagans and shamanic practitioners work with angels.
Regardless of their religious overtones, angels are non-denominational. They are energy. No one can co-opt their energy.
There are different kinds of angels. Your guardian angels are angels. They do not care about your spiritual or religious practice. They are there to love, protect, and guide you.
We are all Spirit.
Angels are extensions of God/Goddess/Source/One. We are extensions of God/Goddess/Source/One. We are One working together on different dimensions.
You are aligning yourself with the love of God/Goddess/Source/One when you call on an angel.
Angels wait for us to call on them when we need guidance.
If you are looking for a resource on angels, try A Dictionary of Angels by Gustav Davidson. It’s a good primer.
Of course, you can ask the angels to send you to the resource right for you.