In some of the templates, I’ve used an image that looks like text. Aerolite and Lightside are examples. The text in both of those headers is actually a PDF image and I did that for a reason. Often if you create large text in the header area, it will inadvertently cover your navigation bar buttons. If you convert the text to a PDF image, then you can mask the text and make the image are much smaller, preventing it from covering your navbar.

You can try just putting text there, but if it does cover your navbar, then please see the article entitled Create Your Own Aerolite Header for instructions on how to create an image version of your text. This article includes a video demo and although Aerolite is used as the example template, the instructions are applicable to any template you’re using.