Why I cant import themes on my wordpress blog?
You haven’t given enough information for anyone to be able to answer that.
Themes need to be placed in your themes folder.
Beyond that, we need more details as to the steps you are following and the theme you are using.
Where is your blog hosted? If it is on wordpress.com, then you can’t upload a custom theme there.
These are all paid themes , so you have to purchase them first and after that it will be installed. But free themes can be installed easily by clicking on them.