Measure the length of your bar using your tape measure. Measure and mark the wood according to this measurement, then cut it to the appropriate length with your table saw.
Enter the information necessary to calculate the cut of your cove using your calculator. Enter the depth you want your cove to be, then divide it by two and hit the "TAN" button. Multiply that figure by 5.5. Divide by 3.88 by the figure you got by multiplying the first product by 5.5, then press the "Inverse TAN" button. This will give you the necessary angle of the miter gauge.
Adjust your miter gauge to the angle indicated by the cove cutting table calculator and secure it to your table saw table using a clamp or the built-in attachment mechanism. Align the piece of wood with the angle created by the miter gauge.
Turn on your table saw and slowly pass the wood across the blade so that it is constantly pressed against the guide created by the miter gauge.
Repeat the cutting process as necessary to create the cove of your bar rail. This can take several dozen passes.
Sand the bar rail as much as possible with a belt sander, then use a palm sander to refine the angle of the cover. Stain or seal the bar rail to your liking, then attach it to the bar using brackets.