Have you gone through the data tables tutorial? Anvil | Data Grids: Displaying Data In Tables
If you have gone through that one, and are still having trouble, you should post some code (in your case the code for the form and the data bindings that you’re using). It’s hard to give specific advice (other than “use this tutorial”) without specifics in what’s going on in your app.
This might also be useful: How to ask a good question