Mor, my brother, I wouldn't worry too much about it--just do what you see others doing. If the church has pews it will be difficult, if well nigh impossible, to do the prescribed prostrations anyway UNLESS you step out into the aisle (as you may see some few doing for this purpose) or you are standing in the back of the church.
At any rate, a full prostration is done immediately after the second Prokeimenon when the priest comes out with a lighted candle, holds it upright and proclaims: "The light of Christ illumines all!"
Another full prostration is done during the censing while the priest and choir (or choir alone) solemnly sing repeatedly (often as a trio) "Let my prayer arise like incense" while the priest stands before the Holy Table censing continuously.
And finally, a full prostration is done during the solemn entrance with the Presanctified Holy Gifts (out through the deacon door and then through the Royal Doors) with the priest saying nothing. Indeed, even the choir is silent for a few moments at this point.
And, oh yes, the Lenten Prayer of St. Ephrem the Syrian is done twice during the Liturgy of the Presanctified Gifts in a typical OCA parish. Just watch the priest and do the prostrations with him at that time.
You'll do just fine, Mor. With an Oriental Orthodox orientation, you'll fit in imperceptibly, Big Guy! The Presanctified Liturgy is made for the likes of us, Eastern and Oriental Orthodox alike.