If these tips didn't help you, maybe it's because you're afraid of having your finger up there. I know I was, and still somewhat am. It's not that I'm afraid of having anything in my vagina, just that I was doing it to myself. That being said, your issue may be psychological, so here's what helped me get my ring out the first few times:
1. Play some music that will relax you, or the TV. Get your mind away from the fact that you've never done this before
2. Maybe have your boyfriend talk to you or be there. Again, this is about relaxation, not about having him do it for you.
3. Finally, what helped me the most was using lubricant on my index finger. maybe you already have some or you could just go to a grocery store and grab some. Find that comfortable position (either squatting, or lying down with your legs up) and see if the lubricant made your finger slide in easier
I know this really helped me, so I hope it works for you!