updated README with more info and installation instructions

README.md

@@ -1,2 +1,30 @@
 # NDRSanalysis
-R package containing functions used by the analysis team within NHS England's National Disease Registration Service (NDRS).
+
+R package containing functions produced by the analysis team within NHS England's [National Disease Registration Service (NDRS)](https://digital.nhs.uk/ndrs).
+
+## About
+
+[![status: active](https://github.com/GIScience/badges/raw/master/status/active.svg)](https://github.com/GIScience/badges#active)
+
+The functions currently available in the package are:
+
+-   **ndrs_prevalence()**: a function used internally on patient level NDRS data, to produce the values presented in the following publication: <https://digital.nhs.uk/ndrs/data/data-outputs/rare-disease-and-condition-prevalence>
+
+### Built With
+
+[![R v4.3.1](https://img.shields.io/badge/R-v4.3.1-blue.svg)](https://cran.r-project.org/bin/windows/base/old/)
+
+## Installation
+
+```         
+# install and load the devtools package 
+install.packages("devtools")
+library(devtools)
+
+# install the NDRSanalysis package
+install_github("NHSE-NDRS/NDRSanalysis")
+```
+
+### Contact
+
+If you have any questions regarding this repository please contact the team mailbox at [nhsdigital.ndrsanalysis\@nhs.net](mailto:[email protected]).