In addition to the individual functions you can also document the whole package.

When you document a package you can use all of the same tags as for functions 
but the problem that you have is that there is no R code to document. 
Instead you put the keyword "_PACKAGE" underneath your package header.

You should also use the @docType and @name tags to indicate that this is package 
level documentation, and specify your package name.

You should then save the package documentation in the R directory in a file 
ending with .R with the same name as the package.