Can you help – I need to upload a Sharepoint 2013 Site Template wsp with powershell?

Hello,
I am using SharePoint 2013 and i want to create some spweb from a site template…

I have created a site and added my desired content and i saved that site as template, then went to solution gallery and downloaded the `.wsp` file.

Now, i need to create a new site collection with some subsites which are based on that template, and to do so i think need to upload the `.wsp` file to the solution gallery the way i can find the newly saved template, and i need to do that from PowerShell !

I tried 2 ways,

First,

I tried to add-spsolution and install-spsolution like following

Add-SPSolution -LiteralPath $SPIntranetTemplateFilePath
Install-SPSolution -Identity SPITemplateFile.wsp -CompatibilityLevel 15 -force
but i don’t find the .wsp in the solution gallery and the template is not in templates list…

I tried to use Install-SPWebTemplate but this command is not recognized as a cmdlet in my PowerShell (I have added `Add-PSSnapin Microsoft.SharePoint.PowerShell`)

I have used this too

## SharePoint DLL
[void][System.Reflection.Assembly]::LoadWithPartialName(“Microsoft.SharePoint”)
Can anyone help me to use my WspFile the way i can create subsites based on my template ?

Thanks