To be able to use the ISE for SharePoint, you can configure it to load the SharePoint cmdlets automatically.
If you only want to use the SharePoint cmdlets once, you can register them with this two lines:
If ((Get-PSSnapIn -Name Microsoft.SharePoint.PowerShell -ErrorAction SilentlyContinue) -eq $null )
{ Add-PSSnapIn -Name Microsoft.SharePoint.PowerShell }