Link: http://www.tagwith.com/question_322855_how-to-pass-parameters-in-powershell-invoke-restmethod-post
Examples: Invoke-RestMethod -Uri http://localhost:49879/api/values -Method Post -Body @{param1=test;param2=test2}
Invoke-RestMethod -Uri http://localhost:49879/api/values -Method Post -Body @{param1=test;param2=test2}