Hi Stumagoo, and welcome to the forum.

You've got a floating bridge on that kit, so there aren't any real worries about positioning the neck for scale length. All you need to really concern yourself with is 1) does the neck centreline line up with the body centreline and 2) Is the neck angle OK so that the bridge height is alright and not too low or too high?

So the best way to test is to clamp the neck in position on to the body. If you haven't got a suitable clamp, you'll need to get one for gluing the neck on. Use cardboard or thin wood between the clamp and the guitar to prevent marking the body and neck.

Then get a long straight edge and place it along each side of the neck in turn, and mark at a spot near where the bridge will go where the straight edge projects to. Hopefully this should be equi-distant from the centreline of the body. Note that the veneer join may not be quite on the guitar's centreline. If it's definitely skewed, then some sanding or shims to correct the angle will be needed. Check twice if you aren't sure and take photos so that we can see the problem.

Then locate the bridge at the point of the body that corresponds to the scale length - tape it down so that you don't need to keep holding it. Adjust the truss rod so that the neck is as straight as you can get it (clockwise for less concave bow, anti-clockwise for more concave bow/less convex bow). Run the straight edge along the top of the neck so that it projects a straight line to where the bridge is. If you can adjust the bridge so that the bottom of straight edge hits about 3mm below the top of the saddle without the bridge being far too high, then you'll fine. If the bridge is screwed down as low as it can go and the straight edge is 4mm or greater below the saddle height, then you'll need to increase the neck angle with respect to the body (or possibly lower the bridge height if it's just a small amount out). If the bridge is far too high to get that distance, then you'll need to decrease the neck angle with respect to the body so that the bridge can sit lower.

However, the bodies and neck are CNC routed, so there's normally no issues with the neck/body join.