It comes from the factory with the tie downs attached to the cross bar on the frame, just in-front of the head, where the engine guard bolts-on. But that only works if your D-rings are placed where the tie-downs won't rub on the fender or lower fairings (if you have them).
When traveling to destinations that are +1,000 miles away and the wife is accompanying, I have to trailer due to my wife's back problems. My trailer has a roll-on wheel chock, so my primary need is for the tie-down to pull the bike forward to lock-in the front wheel. I use a tie-down attached to the rider floorboard mounting bracket to create that force, then use a second set of tie-downs on the saddlebag guards, as close to the lower mounting bolt as possible, again pulling the bike forward (as opposed to just trying to secure the rear-end). The lower side of the saddlebag guard has a horizontal cross bar that keeps the tie-down from slipping down to the outer curve of the guard where it might create enough pressure to bend the guard. In both cases, I use tie-downs with the spring loaded latch on the S-hooks so that they don't fall-away if the trailer has a hard jolt. If your tie-downs don't have the latch, you can tape then to accomplish the same effect. Don't ask me how I learned about S-hooks slipping off...it's still too painfull to discuss in public.
On my Ultra Classic and Ultra Limited, I had installed the tie-down brackets on the front forks. Those work really well, but cannot be mounted on the Road Glide due to the fixed faring. Darn shame.
If life throws you a curve...lean into it!