Figured post the code I edited to get it to work based on the link I posted above.
function Upload-JiraCSV($jiraTicket, $filepath)
{
$wc = new-object System.Net.WebClient
$wc.Headers.Add("Authorization", $headers.Authorization)
$wc.Headers.Add("X-Atlassian-Token", "nocheck")
$wc.UploadFile("$URIPath/issue/$jiraTicket/attachments", $filepath)
}