How to change function pointers?

[NoHero]

I think it is the best to use an example:
I have a hook DLL which is in the address space of mspaint.exe for example. If you open a file in mspaint GetOpenFileNameW() function from COMDLG32.DLL will be called. Instead I want now to call my OpenFileName() function which is in my hook DLL, in order to show my custom open dialog with preview functionality. I only know I need to change the import address table. But I don't know in which memory location it is.

This is your article...