If your OEM selector rod has a bend, you may need to replicate that bend for proper fitment in your car. This process is very straightforward and all you need is a vice and some sockets.
Arrange your sockets as shown in the photos below with the larger socket on the bottom. Make sure your DSSR is perfectly flat because if you bend it at an angle, then it may effect fitment in your car. Carefully and slowly tighten your vice until you nearly match the bend in the stock selector rod.
If your DSSR gets "kinked", see photo below, do not worry because even some OEM BMW selector rods are manufactured with a similar "kink".
Top - Garagistic DSSR
Bottom - OEM BMW Selector Rod