Add field to SharePoint ;ist

PowerShell Script

Add-PSSnapin Microsoft.SharePoint.PowerShell

[Microsoft.SharePoint.SPSecurity]::RunWithElevatedPrivileges(
    {
        $site = SPSite("http://siteurl/")
        $web = $site.RootWeb
        $spList = $web.Lists["List Name"]
        $spFieldType = [Microsoft.SharePoint.SPFieldType]::Boolean
        $spList.Fields.Add("Field Name",$spFieldType,$false)
        $spList.Update()
    }
)