As soon as you are injected, youll be able to directly execute scripts in the Roblox lua environment

Execute

Put this code in your Execute_Click() event.

private async void execute_Click(object sender, RoutedEventArgs e)
{
    Api.execute("print('Hello, World')"); 
}

Replace print('Hello, World') with the actual Lua code.

Usually, people want their executor to run custom scripts, not pre-set ones, but rather text from an editor. Here is an example for richTextBox1

private async void execute_Click(object sender, RoutedEventArgs e)
{
    Api.execute(richTextBox1.Text);
}

this code will use the content of the richTextBox1