Install PSM 1.00
You need the following files from "C:\Program Files (x86)\SCE\PSM\tools\lib"
host_transport64.dll
psm_device64.dll
From "C:\Program Files (x86)\SCE\PSM\tools\PsmStudio\AddIns\MonoDevelop.Debugger.Soft"
Mono.Debugger.Soft.dll
From "C:\Program Files (x86)\SCE\PSM\tools\PsmStudio\bin"
Mono.Cecil.dll

Put them all in .\VitaInjector\lib\

Building VitaInjector:

First build VitaInjector (Debug) by building .\VitaInjector\VitaInjector.sln
Next build the loader client (Debug) by building .\LoaderClient\LoaderClient.sln
Rename .\LoaderClient\bin\Debug\LoaderClient-unsigned to LoaderClient
Copy LoaderClient to .\VitaInjector\bin\Debug
Copy contents of .\VitaInjector\lib\ to .\VitaInjector\bin\Debug

Signing the package

On PSM 1.00 you need to sign stuff. First, become a paying publisher.
Then create a keyring for "*" and run any sample app to "load" the key unto the Vita.
If the sample app runs, you can use VitaInjector. If not, find out why.
Then VitaInjector should work as usual.

Running VitaInjector:

Open the PSM dev app on the Vita and plug in the USB.
Open device manager and see what serial port the Vita's using (COMX will be used here)
To dump memory, run with:
    VitaInjector.exe d 0x81000000 0x100 dump.bin COMX
                       ^ address  ^ len ^ output ^ port
To run an unencrypted SELF or (recommended) ELF:
    VitaInjector.exe l homebrew.elf COMX
                       ^ app        ^ port