The lack of drill holes for the bridge can be an advantage, as it means you can fit whatever bridge you want. Whilst there are generally standard fixing hole arrangements for guitar bridges, bass bridges come in all shapes and sizes and with varying numbers of screw holes. So having holes pre-drilled for the bridge that came with the kit (if there was one) might mean that you'd have to fill those holes if you wanted a better bridge with a different number of screws - or they might even be on display with another bridge fitted, and spoil the look.

It's not hard to locate the bridge position. First you need to draw the centreline for the guitar. Bolt the neck in place, get a long stiff straight edge, place it along each side of the neck and draw pencil lines back to the area where the bridge will be. Use light pencil strokes as you don't want to gouge the wood, and you'll need to sand the marks off later.

Draw lines that cross the body at right-angles to the (as yet undrawn) centre line (the pickup routs should be perpendicular to the centre line as well, so use the as guides) near the neck and at the bridge end of the guitar. Measure the distance of each crossing line between the two lines you first drew, halve the distance and draw a dot at each midway point. Now connect the two dots with a line and that should be the centre-line for the guitar (as determined by the neck).

You can now measure the bridge, and mark with a thin felt-tip (or anything that will put a mark on the metal) at the half-width point of the bridge at the neck-end and tail-end of the bridge. You can now put the bridge down on the body so that the middle is sitting on sitting on the initial centreline. You know the scale length of the guitar, so you can measure roughly 34" (or whatever the scale length is supposed to be) from the nut to the bridge saddles position, and move the bridge so that it's roughly in position with the saddles in mid-adjustment position. I'd use the Stewmac calculator (on their website) to work out the exact length away from the nut that the top G string saddle (in it's mid position) should be from the nut. Mark the top and bottom position of the bridge on the guitar with pencil.

Keeping the bridge in position (maybe using double sided tape), I'd run a piece of string from the bottom E slot to its saddle, and from the top G slot to its saddle. Hopefully the strings should run nice and parallel to the sides of the neck without getting to near or too far from the edge. If the strings look skewed to one side, then you'll need to move the bridge sideways a bit until they aren't. Hopefully the strings should now run nicely either down either side of the neck and as close as you can get to either side of the pickup cavities. You can always place the pickups in the cavities if this helps (as the cavities may not be exactly the right shape and it's the way the strings pass over the pickup that will matter most).

Once this is done, mark either side of the bridge on the wood and you've now positioned your bridge. Mark out the screw holes, then drill the holes (remembering just to drill to the depth of the screws). Best to test out the position of the bridge again once it's screwed into place, in case something went horribly wrong with your drilling. But if you are then happy with the location, you can then clean up the pencil lines and relax.

Don't forget to fit the bridge earthing wire before you fit the bridge for the final time.