Now that I have all the stocks that respect Graham rules, how should I select the one I want to invest in?

I think any answer to this one is going to be in the realms of personal preference.

I can think of a couple of approaches. Graham was all about having a margin of safety, preferably more than one, i.e. the stock should have a low valuation compared to book, it should have low debts, be cash generative etc. So pick one.

If you're looking to max out your margin of safety then perhaps you would choose to preferentially buy companies with as low a price/tangible book value as possible.

Larger companies tend to be safer so you could sort by order of size. A larger company, all else being equal, should have more cash and a better market position and be better able to wait out or buy out any problems that arise.

If you want to max out the amount you're making while you wait for the price to come up then sort by yield and buy that way.

And don't forget the other aspects of portfolio risk management, diversify your assets and asset classes and so on.