The SVAC is a friendly group of enthusiasts, but your first match can still be nerve wrecking because of the unknowns. Rest assured that you will be fine! The match director help pair up new comers with a friendly and knowledgeable person.
Although a field target match is a match, just enjoy yourself and do not worry about the points!
If possible, contact the match organizer(s) ahead of time. This way, the club may be able to arrange loaner equipment such as air rifles, stools and etc. Of course, you can also simply bring your own rifle (as long as it has than 20 foot-pound of muzzle energy), show up, and have a good time!
If you are concerned about the muzzle energy of an air rifle, you can discuss with the match organizer and make sure that your rifle does not produce more than 20 foot-pound of muzzle energy.
Generally speaking, for people without prior experience, the hunter division is a good place to start. In this division, a shooter can sit on a stool and use a bipod to help with aiming and shooting.
If this is where you want to start, be sure to read A beginner's guide to hunter division shooting!