Do you want to login into Blogspot .com to access blogspot login page for sign up with blogspot to create a blog? The blogspot is actually a domain name in Blogger, when you create a blog in blogger .com with any name then the blogspot would be added automatically to that name. For example you created a blog with name mycookingrecipes then the full name of your blog would be mycookingrecipes.blogspot.com.
So if you want to login into blogspot to access a blog or to sign up with blogspot, then you have to login into blogger.com. Blogger is a Google's product in which you can create a blog for free. You can use the following link to login into blog spot.