Buy Time-Trial bIke or convert road bike
The geometry is the major problem with converting a road bike into a TT/Tri bike, road bikes have you sitting much farther back relative to the contact points on the handlebars.

You may be able to offset this with a different seatpost that puts you farther forward (assuming saddle is adjusted all the way towards the front). 

Other changes may include a shorter stem, different saddle. 

You may be able to make your road bike work, just don't expect to be comfortable mid ride switching from the aerobars to the hoods/drops. You have to pick one and stick with it.