The four-step pattern you learned still applies:
Define the state. What does represent? Write it in plain English.
Find the transition. How does relate to smaller subproblems?
Set the base cases. What are the simplest subproblems you can answer directly?
Extract the answer. Which cell (or combination of cells) gives the final answer? Nothing changes except you have more indices. If you can do 1D (one-dimensional) DP, you can do 2D (two-dimensional) DP.