Hi, can anyone help me on it? I can't go through and download the video from R18.com. Thank you

You are using PowerShell. You need to put .\jav-it to launch the exe. Also, the options are called with a "/", not a "-" (in the non-patreon version I have).

PS > .\jav-it download /c r18.com_cookies.txt /i soe195 /o c:\downloaded