How do i cook pizza dough before adding toppings?
So we have two different things here: first, can you precook your pizza crust, and two, why is your pizza crust coming out "underdone" when you cook it with toppings.

Of course you can precook pizza dough.  Just roll it out, and put it in the oven for somewhat less time than you would for a finished pizza.  For example, if cooking a pizza with toppings normally takes 12 minutes, parbake the crust for around 5 minutes.

The second question, though is why is this a problem for your pizza dough in the first place?  I'm going to assume by "underdone" you mean "doughy and wet", because that's the usual problem with poorly-cooked pizza (aside from burnt, which is the other end of the spectrum).  There's a few common reasons why your pizza crust would come out doughy and wet:


Too many toppings: if you have a thick layer of heavy toppings, the heat cannot penetrate to finish cooking the crust.  Use fewer toppings
Toppings are too wet: fresh tomatoes, raw mushrooms, watery tomato sauce, uncooked leafy greens, and other "wet" toppings give off a lot of water when cooking, and can cause your crust to be soggy.  The solution is to pre-cook these toppings before adding them.
Dough is too thick: if you are making a pizza crust with a really thick layer of dough, like over 2cm, then it will take a long time for it to cook through.
Oven isn't hot enough: pizza needs to be cooked in an oven that's at least 225C, and better if it's 300C or higher.  If your oven is at a lower temperature, or if there is no heat coming from the bottom, then the dough may never completely cook.
You're making pizza in the microwave.  I suggest this based on some of your other questions.  Making pizza in the microwave doesn't work, and you cannot make it work.