PSRAW-Send-PM-Example.ps1

Install-Module PSRAW -Scope CurrentUser
Import-Module PSRAW

# Go here https://ssl.reddit.com/prefs/apps
# use https://127.0.0.1 for redirect uri
# register Script App and note client id and secret

Connect-Reddit

$Params = @{
    Uri = 'https://oauth.reddit.com/api/compose'
    Method = 'POST'
    Body = @{
        'api_type' = 'json'
        'subject' = 'Test Message'
        'text' = 'This is a test from PSRAW!'
        'to' = 'SomeRedditUser'
    }
    ContentType = 'application/x-www-form-urlencoded'
}
$result = Invoke-RedditRequest @params