Update README.md

Author: SweetIceLolly

README.md

@@ -1,4 +1,67 @@
 # VB6 MemoryDC
 A memory DC class written in VB6. You can use this class to create and operate memory DCs easily.
 
-#Usage
+# Usage
+
+## Initalizing MemoryDC class
+
+To declare a MemoryDC typed variable, simply
+```VBS
+Dim memDC As New clsMemDC
+```
+
+Next, you should create the DC when you need it:
+```VBS
+memDC.CreateMemDC image_width, image_height
+```
+For function `CreateMemDC`, please refer its description in "Functions Description" section.
+
+## Deleting MemoryDC class
+
+When you no longer need the MemoryDC typed variable, simply
+```VBS
+memDC.DeleteMemDC
+Set memDC = Nothing
+```
+
+## Painting from other DCs
+
+To paint the image from other DCs, simply
+```VBS
+memDC.BitBltFrom YourDC, FromX, FromY, ToX, ToY, image_width, image_height
+```
+
+For function `BitBltFrom`, please refer its description in "Functions Description" section.
+
+## Painting to other DCs
+
+To paint the image to other DCs, simply
+```VBS
+memDC.BitBltTo YourDC, ToX, ToY, FromX, FromY, image_width, image_height
+```
+
+For function `BitBltTo`, please refer its description in "Functions Description" section.
+
+## Copying bit data to a Byte array
+
+To copy the bit data of the image in the DC to a Byte array, simply
+```VBS
+memDC.CopyDataTo data     'data is a Byte() typed array variable
+```
+
+For function `CopyDataTo`, please refer its description in "Functions Description" section.
+
+## Copying bit data from a Byte array
+
+To copy the bit data of the image in the DC from a Byte array, simply
+```VBS
+memDC.CopyDataFrom data     'data is a Byte() typed array variable
+```
+
+For function `CopyDataFrom`, please refer its description in "Functions Description" section.
+
+## For more functionalities, please read the following sections.
+
+# Functions Description
+
+# Property Description