Update README.md

Author: eduard93

README.md

@@ -3,16 +3,27 @@ Python adapter via callout for InterSystems Data Platforms.
 
 # Installation
 
-1. Load ObjectScript code from [here](https://github.com/intersystems-ru/PythonAdapter/blob/master/isc/py/Callout.cls).
-2. Place DLLs in `bin` folder.
+1. Load ObjectScript code.
+2. Place callout DLL in `bin` folder.
+3. Check that your `PYTHONHOME` environment variable points to Python 3.6. 
+4. Check that your SYSTEM `PATH` environment variable has PYTHONHOME.
+5. Execute: `do ##class(isc.py.test.CannibalizationData).Import()` to populate test data
 
 # Use
 
+1. Call: `do ##class(isc.py.Callout).Setup()` once per systems start (add to ZSTART!)
+2. Call: `do ##class(isc.py.Callout).Initialize()` once per process
+3. Call main method (can be called many times, context persists): `write ##class(isc.py.Callout).SimpleString(code, data)`
+4. Call: `do ##class(isc.py.Callout).Finalize()` to free Python context
+5. Call: `write ##class(isc.py.Callout).Unload()` to free callout library
+
 ```
+do ##class(isc.py.Callout).Setup() 
 do ##class(isc.py.Callout).Initialize()
 write ##class(isc.py.Callout).SimpleString("x='ПРИВЕТ'","x")
 write ##class(isc.py.Callout).SimpleString("x=repr('ПРИВЕТ')","x")
 write ##class(isc.py.Callout).SimpleString("x=123","x")
+do ##class(isc.py.Callout).Finalize()
 write ##class(isc.py.Callout).Unload()
 ```