As a resident Mudcat Mando-Idiot, I'd be happy to help out. I'd recommend a nylon pick with a decent grip, e.g. Dunlop or similar, of about .60 or .73 thickness, depending on your preference (I prefer the thinner). It is important to be quite relaxed when playing, therefore not too tight a grip is preferable. Various hand positions are possible, all of which have their pros and cons. I tend to rest the ball of my hand just behind the bridge (frowned upon by many but it has worked for me for 40 years) with my hand more or less parallel with the strings and the pick help at right angles to the hand between thumb and index finger.
Hope this starts you off OK...don't hesitate to asl for help. The site below via click blue thing is a Mando-Idiots's dream (I believe you have landed us poor souls with a label that will stick Dear Aine!):
Happy picking and good luck!