adding usage to readme

instrgen/README.md

@@ -6,6 +6,32 @@ This package provides a code generation utility that instruments existing source
 
 :construction: This package is currently work in progress.
 
+## How to use it
+
+In order to instrument your project you have to add following call in your entry point function, usually main
+(you can look at tests directory for reference) and invoke instrgen tool.
+
+```
+func main() {
+    rtlib.AutotelEntryPoint()
+```
+
+Instrgen requires three parameters: command, path to project and package(s) pattern we
+would like to instrument.
+
+```
+./instrgen --inject [path to your go project] [package(s) pattern]
+```
+
+Below concrete example with one of test instrumentation that is part of the project.
+
+```
+./instrgen --inject ./testdata/basic ./...
+```
+
+```./...``` works like wildcard in this case and it will instrument all packages in this path, but it can be invoked with
+specific package as well.
+
 ### Compatibility
 
 The `instrgen` utility is based on the Go standard library and is platform agnostic.