Yes, once your license plate has been entered into the official Slovenian toll system, your e-vignette is activated and you can legally drive on Slovenian motorways and expressways.
Please note, that after the confirmation email you will receive the vignette in a separate email.
Related articles:
Do I get a confirmation email for my Slovenian vignette order?
Where can I check the status of my Slovenian e-vignette?
How long is the Slovenian vignette valid?
Do I need a payment receipt or print-out of the Slovenian vignette?
I bought the Slovenian digital vignette but got no email, what now? (Vignetteslovenien.si)