Update CONTRIBUTING.md

CONTRIBUTING.md

@@ -29,10 +29,20 @@ This document provides guidelines for contributing to this repository.
 - Update the README or other documentation if necessary.
 - Clearly describe the changes you've made and their benefits.
 
-## Contributing to the R Package
+## Contributing to the R Package - author or reviewr of a PR
 
-If your contribution involves changes to the R package itself, here are some specific guidelines to follow:
+If your contribution involves changes to the R package itself (author or reviewer of a PR) here are some specific guidelines to follow:
 
+1. Clone this GitHub repository and ensure all branches you need are up to date with remote.
+2. Open up R Studio and ensure you have a **Git** tab in your workspace.
+3. In this **Git** tab, move to the branch you want to make changes in (or review and test the changes of someone else).
+4. Ensure that your current working directory is the R package directory you cloned (`getwd()` to check and `setwd()` to change).
+5. Run `devtools::load_all()` in the R console. You should see `ℹ Loading browseMetadata` returned.
+6. Test the function runs by running `domain_mapping()` in the R console.
+7. Make your changes (or review changes made by others), and commit these changes in the way you choose to interact with git locally!
+
+If you run into issues with branches not seeming to be up to date in the R Studio workspace, consider running `remove.packages("browseMetadata")` and trying the above steps again, in case a previously installed package library is getting in the way somehow. 
+
 ### Working with Package Data
 
 - **Creating .rda Files**: To create `.rda` files in the data directory of the package, use the following command in R: