Here is a small PowerShell script to Export all users in your tenant along with the licenses assigned to them in O365.
To Execute this you must have MSOL PowerShell module installed which you can install by running following command
Install-Module MSOnline
Once its installed run following script
#Establish a PowerShell session with Office 365. You'll be prompted for your Delegated Admin credentials
if (!$UserCredential)
{
$UserCredential = Get-Credential
}
Connect-MsolService -Credential $UserCredential
Get-MsolUser -All | select DisplayName,USerprincipalname,islicensed,{$_.Licenses.AccountSkuId} | Export-CSV C:\<FileName>.csv