If you want to use additional files inside your "program" function, you can simply add these files inside your submitted zip file. They will be available in the working directory when your code will be sourced.
Example :
. inside the zip file "program_p1.zip" you have :
. program.R
. metada
. temp.rds
. inside the function "program" (from program.R) you can have :
. temp <- readRDS("temp.rds")