If it's your third workout, it doesn't matter. The weights shouldn't be heavy enough to make a difference if you started with the bar (or 95 pounds on the deadlift). These sessions are just for gradually ramping up the weight while working on technique.
Just get back on schedule as if the missed workout never happened. I prefer to lift again ASAP, but skipping it and just doing the next normally scheduled day is fine too.
Taking the squat as an example:
- Saturday: squat 45
- Monday: squat 55
- Wednesday: oops!
- (Thursday): go ahead and squat 65, or rest
- (Friday): you could also squat 65 here--it's not a big deal, the weights are light--or rest. The rest is almost certainly not necessary, since you haven't started lifting heavy yet.
- Saturday: either squat 75 if you worked out Thursday or Friday, or squat 65 if you didn't