I had the same thing happen to me and then one day I was put in a situation where the my only option was a tampon and so I just read the instructions in the box, figured it out and I have used them ever since. I told my mom that I started using tampons and she told me everything I needed to know and o was glad I told her afterwards :)
If you really don't know how to approach your mom about it, maybe talk to a close friend or older family member who you trust
Try to search on youtube on how to use it if you're not comfortable with asking your mom :) or try asking your older sister if you have one :)
I wasn't completely comfortable about asking my mom about that stuff, Ive had my period for 2 years now and I still don't really. instead I asked my older sister and I felt a lot more comfortable talking with her.
I had the same fear for a while. I'm 14 and I finally asked my mom about it last year. Just don't over think it, she's been in your position before. It may be awkward but at least you'll know how to use one and you won't have to ask again.
Just talk to her she was a young lady before to so she will understand