Iwant gmail on the top of my computer when i turn it on

Usually you open a browser to see your mail.
You can set the browser to open to the Google mail page, so open
the browser to make that setting. After you open Google mail,
for Internet Explorer you can click the tools icon at the upper right.
In Tools, click internet options. It will open to the General tab.
In the Homepage section, click Use Current. Google Mail will be
your home page.
For Firefox, open it and go to Google Mail. Then click the Menu
Icon in the opper right. Click Options. Options should open on
the General tab, showing Homepage already selected. Click on
Use Current Page.
Those procedures won't open your operating system to Google
mail, but it will appear as soon as you click on your browser.