How do I get custody of my grandson that I have had for almost 2 years?

You need to start by filing a custody suit and then requesting final orders that formally give you custody, and if you would like, that require the parents to pay child support to you for the child.  Custody matters are often hotly contested, but considering that neither of them come around to visit or provide support, consider having a family law attorney draft up some agreed orders and see if they will sign off on them.  It will make the process much quicker and smoother if you have an agreement going in.