Naming a blog can be a tricky thing as the name you originally chose for your blog might not make sense when you look at it after a few days , although naming your blog should be done carefully in the beginning but for some reason if you want to change your blog name you can do so in the settings of your blogger dashboard.
Login to Blogger with your credentials and you will have access to your dashboard.
Select the blog whose name you want to change (Drop down from top left corner).
Go to the settings tab and there you will see options to edit details about your blog like Title , description and Blog Address.Simply change the blog address and/or title of blog and save your changes.
If you have a fairly new blog then changing your blog address won't affect your blog much as the your blog will start ranking with the new url but if you have been blogging for a while then maybe it would be better if you avoid changing blog address frequently as this can affect your blog's ranking in search engine and your blog won't be