If you are trying to display the posts on your blog with a specific tag then it should not be an issue, for example, I can type into the address bar this URL for my home site: http://buynowshop.com/tag/cais and press enter. It will display all the posts with the ‘cais’ tag. (The site default theme does not use a tag.php template, currently.)
If you are trying to do something else, perhaps you could provide some more details. Also, your blog URL may be helpful as well.