Of everything I've gathered from this site, one recurring theme is that there is no religious discriminations or requirements. The paraphrase "choose the path that feels right to you" comes up a lot, too. This site has a wide array of practitioners from all religions and walks of life. You don't need to absolutely believe in one thing or another to use this site or the content of it. I'm still doing my share of research, myself, before I go ahead and make any religious commitments. Before that time comes, if or when it does, I'll be sticking to my omnist views and still believe the spells, rituals, and information on other topics to be possible and those of which I've experienced personally to be true.
In short, you've got nothing to worry about. You're just as free to use the site and its content as anyone else is regardless of religious views. If a spell you want to try talks about spirits or deities you may not believe in, substitute that aspect for something you do or can believe in. It's worked for me before and I'm sure it's worked for others as well.