The first thing you need to do is arrange your Grapewood Branches in a way that it will make the candelabra as stable as possible. It is rare that you'll find a single Grapewood Branch that's stable in all directions, and this is why you need to use more than one (we used two). Obviously, you do not want this thing tipping over. Try tipping it in every possible direction, and rearrange until you get a stable configuration. Once you've done this, secure the branches together at their contact points with cable ties (a set of pliers would be useful here to pull the cable ties tight).
Next, it is time to permanently secure the branches together with your wood screws. You'll probably want to drill a small pilot hole through the branches, as Grapewood is fairly hard. We actually used coarse-thread drywall screws, but the bite of these was a bit too aggressive.
Now it is time to glue the nails onto your tea light holders, votive holders, or whatever it is you've chosen to use. First, clean the bottom of them. Then turn them upside down, put a dab of the super glue gel on the nail head, and stick it on. The more glue the merrier. The super glue gel sandwiched between the metal heads and the glass takes quite a while to set, so you should leave these overnight. After the glue has had plenty of time to set, give the nails a good wiggle to make sure they are secure - you are likely to have one or two that don't have a strong bond, and now is when you want to find this out - not when you have a lit candle in it or a vase full of water. This is especially important with heavier items, such as bud vases, which when filled with water and flowers will put the most strain on the bond.
Next up, start drilling the holes into your Grapewood. Pick a drill bit that is just a hair bigger than the nail. As for where to drill, pick spots that are level and drill straight down. This is the trickiest part of the operation. You'll likely end up with a few holes that angle a bit away from vertical, but you'll also have some holders or vases where the nail isn't quite glued on straight - match these correctly (rotate the vase or candle holder), and they will sit (more) level.
Add your tea lights, votives and/or flowers and you have a stunning and unique centerpiece that will surely get a lot of attention!