Hello BlondeFairy: Well... there are perhaps a couple of different ways to look at this. One is to simply see it as a challenge & "walk toward what scares you..." (There's a story behind that phrase. But I won't bore you with it.)

The other possibility is to simply be honest, with whomever is in charge (the PTO President?), about where you're at with regard to the skills you'll need to be an effective secretary. Let her / him know that you're anxious to continue on as secretary but that realistically it may take some time for you to get up to snuff, as we used to say. This will let the President of the PTO know where you're at with regard to this & hopefully it will take a bit of the pressure off of you.

One alternative might be to "job share" with another member so not all of the responsibility falls onto you right off the bat. But also, you may find that in reality you're expecting more of yourself, than others in the group are going to expect of you. Really, this is a volunteer organization & no one should, at least, be expecting you to perform like an experienced administrative assistant. At least these are my thoughts with regard to your post.