Once you have loaded the DataSHIELD packages, information about individual functions can be found on the function manual page including:

description: what the function does
usage: shows the syntax of the function including all arguments - this is a generalised form of how you would use the function
arguments: of the function. These are all the things you can customise in the function
details and values: give some additional information about the function
examples: of how the function is run. You will be able to copy and paste these examples into R/RStudio to run yourself

You can access the help page of a function in a number of ways:

Opening help files in R

To open up the help page within R/RStudio:

> help(insert_function_name)
# an example for ds.histogram
> help(ds.histogram)

an equivalent command is to use the help operator ?:

> ?(ds.histogram)

Opening up help webpages

To open up the function help page in a webpage:

> options(help_type="html")
> help(ds.histogram)
# alternatively use
> ?(ds.histogram)

An example function help webpage for ds.histogram is given below.