This plugin registers a module in the blender python environment which can perform arbitrary Map Projections. The plugin makes use of pyproj in order to perform these projections. To learn more about projections and why the are useful, I encourage you to read this.
Pyproj relies upon a binary dependency, Proj4, requiring this plugin to distribute these binaries. This plugin will attempt to expose these binaries to the embedded python environment.
Download the addon from here, install and activate it as an ordinary Blender addon. Follow these instructions if you have never installed a Blender addon.
This plugin will attempt to automatically install the pyproj dependency upon startup. A message will appear in the log if there is any error.
Spatial Reference Identifier (SRID) is a code that tells the plugin which projection system you desire to work with. A list of common SRID's can be found here at EPSG.io. Simply type in the SRID (e.g. EPSG:3857) into the SRID field.
If more granular control is needed you can change the drop down menu (Specify Projection) from SRID to Proj4 Params. You can now input the Proj.4 parameter string directly in the field titled Proj4 Parameters.
Read the dedicated wiki page.