If you already have a Google account (i.e. Gmail, Blogger, Adwords) then you can use that username/password to access the webmaster tools.

• Register and/or Login to http://google.com/webmastertools
• Click My Account (upper right)
• Click Webmaster Tools (right)
• Add your site URL in the box just under "Dashboard" (www.yoursite.com) & ADD SITE
• Click VERIFY YOUR SITE in the highlighted box
• Select "UPLOAD AN HTML FILE" as your method

At this point you will be provided a filename ending in HTML.

• Copy the filename provided
• Open notepad on your system (Start > Programs > Accessories > Notepad)
• Click File > Save As
• Paste the filename you copied into the box (Ctrl+V) , select "ALL FILES" as your file type, and save it to your hard drive.

You'll now need to upload this file to the root directory of your site. Click HERE for instructions. Once you've uploaded the file, return to Google Webmaster Tools where you left off:

• Click Verify