How to pass dataobject that is created in one form into another form?

Since your question is not very clear, I assume that your data object is a data table, and You have two win forms FORM1 and FORM2.

As I understand you have DataTable object (dtForm1) built in FORM1 and you want dtForm1 to be available for FORM2.

Create A static Class called DataTransHelper like below:

public static class DataTransHelper
{
public static DataTable dt {get; set;}
}

In Form1 as soon as you build object dtForm1, you set this to "dt" of DataTransHelper like below.

//dtable = YourDataAcces.GetData();
DataTransHelper.dt = dtForm1;

Since DataTransHelper class is static, it is not instance specific, hence members of DataTransHelper are same to both FORM1 and FORM2.

So in Form2, you can access DataTransHelper.dt and use it as you need it like below.
DataTable dtForm2 = DataTransHelper.dt;