Update readme.

README.md

@@ -2,7 +2,7 @@
 
 Data and code for analysis at https://mastodon.radio/@W1CDN/111723969200676208.
 
-I'll get a blog post up at https://w1cdn.net at some point.
+Introductory blog post: https://w1cdn.net/2024/01/us-ham-radio-license-counts-over-time/
 
 This is a work in progress. It is not intended to be immediately useful for
 detailed analysis, but to act as a guide for further investigation. As we figure out
@@ -19,6 +19,17 @@ how to slice up and caveat data, it will get more organized.
 - FCC numbers as images of tables: https://sites.google.com/site/amateurradiodata/home
 - K8VSY's per capita estimates: https://k8vsy.radio/2021/09/ham-radio-licenses-us-states-per-capita.html
 
+# Contributing
+I am trying to stage new data in the [issues](https://amiok.net/gitea/W1CDN/ham-radio-licenses/issues) list,
+then copy that data into tabular format at a later date. 
+
+If you want to help, here are some ways:
+- look at the issues and copy data into tabular format, share back in CSV format or pull request
+- find new sources and create an issue for each new chunk of data (use best judgement)
+- download data and QC: look for potential errors and inconsistencies, share those in a new issue
+- download data and run analyses: share your interpretations
+- choose your own way to contribute!
+
 # Rough Plots
 ![Alt text](plots/total-over-time-y.png)
 ![Alt text](plots/total-over-time-2000.png)