Docs: add explanation about COM model to how to

docs/HowTo.txt

@@ -450,3 +450,26 @@ e.g.
     # Select an item in the popup menu
     outlook.PopupMenu.Menu().get_menu_path("Cancel Server Request")[0].click()
 
+
+
+COM Model
+------------------------------------------------------------------------------------
+By default, pywinauto sets up the client Multithreading COM model (MTA) on init if
+no other model was defined prior to import of pywinauto. The model can be set up by
+another imported module implicitly or specified explicitly through ```sys.coinit_flags```
+
+Example for settinpu single threaded appartment model explicitly.
+
+  ::
+
+   import sys
+   sys.coinit_flags = 2  # COINIT_APARTMENTTHREADED
+
+   import pywinauto
+
+
+Notice that final value is assigned back to sys.coinit_flags. This is to avoid conflicts with
+other modules. Possible values for sys.coint_flags:
+0 - Multi-Threaded Apartment model (MTA)
+2 - Single-Threaded Apartments model (STA)
+