Download both 0.4.5 and 0.5.1 and unzip both of them.
Navigate into the 0.5.1 unzipped folder until you see the executable LeapofFaith.exe.
Use CTRL+A to select all files and folders (including the game, renpy and lib folders) and CTRL+C to copy.
Navigate into the 0.4.5 unzipped folder until you see the executable LeapofFaith.exe
CTRL+V to paste the copied contents. You should be prompted with a "do you want to overwrite" for a lot of files. Click yes to overwrite.
Run the game from the 0.4.5 folder - which is now patched to 0.5.1 (should display so in the upper right hand corner of the main menu).
If this doesn't work for you, feel free to ask for more help should you need it. :)