How to I activate at TabPage that I choose by coding.
I mean want to show form that contains some tabpages on the exacly tabpage ?? It always show the tappage whose index is the first index.

There are a few ways to do this, I'll show you two:

You simply set the SelectedIndex property of the TabControl object you are working with the index number of the TabPage you want to display.

TabControl1.SelectedIndex = 0 ' First Tab
TabControl1.SelectedIndex = 1 ' Second Tab
TabControl1.SelectedIndex = 2 ' Third Tab

OR you can set the SelectedTab property to the TabPage you want to jump to.

TabControl1.SelectedTab = TabPage1 ' First
TabControl1.SelectedTab = TabPage2 ' Second
TabControl1.SelectedTab = TabPage3 ' Third

NOTE in the second example, 'TabPage1' is the name of the page objects itself. You might call your objects something else.