Windows Powershell Not accepting build.ps1

[AnimeniacSimey]

Windows Powershell doesn't accept ".\build.ps1".

.\build.ps1 : The term '.\build.ps1' is not recognized as the name of a cmdlet, function, script file, or operable program. Check the spelling of the name, or if a path was included, verify that the path is correct and try again. At line:1 char:1

• .\build.ps1

• 
  + CategoryInfo          : ObjectNotFound: (.\build.ps1:String) [], CommandNotFoundException
  + FullyQualifiedErrorId : CommandNotFoundException