After installation, please read the help page:
help("fritools2-package", package = "fritools2")#> Utilities for the Forest Research Institute of the State
#> Baden-Wuerttemberg
#> 
#> Description:
#> 
#>      Miscellaneous utilities, tools and helper functions.
#> 
#> Details:
#> 
#>      You will find the details in
#>      'vignette("An_Introduction_to_fritools", package = "fritools2")'.You can install fritools2 from gitlab via:
if (! require("remotes")) install.packages("remotes")
remotes::install_gitlab("fvafrcu/fritools2")