To your question, "How to edit and change code in dll file using vs 2008.", as stated by naman_goel earlier in this thread unless you have the source code for the ell you wish to modify you will not be able to modify it.
To your question, "and how use it in vs2008", now once you have the source code and modified it, you need to follow the correct steps in using it in your .Net program. For example if it is com, C++ or .Net dll all have different step.
Most important question, Do you have the source code?
Naman Goel
your dll is .net dll, please see the output from coflags
C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC>corflags C:\Users\Viaan\D
esktop\[Megafileupload]LicenseUtility.dll
Microsoft (R) .NET Framework CorFlags Conversion Tool. Version 4.0.30319.17929
Copyright (c) Microsoft Corporation. All rights reserved.
Version : v2.0.50727
CLR Header: 2.5
PE : PE32
CorFlags : 0x3
ILONLY : 1
32BITREQ : 1
32BITPREF : 0
Signed : 0
so again you need source code to edit the dll, you can check the source code by using some de-compiler tool line .net reflector.
Please give us more details if you want help from us...
Merry Xmas!