It sounds like you've created a button but want to make it do something on click. I don't often use Winforms but from memory double-clicking on the control in the form should automatically create a btnTest_Click method. If not, just go to code and put in a method like:
protected void btnTest_Click(object sender, Eventargs e)
{
//do something
}
Then set in the properties of the button the OnClick event to btnTest_Click.