Wait for the upload process to finish, you see the uploaded images and then you have to publish those by clicking the Publish button.

After publishing, you can edit the gallery as per your choice like how many images are displayed in a row, transition effect, height margin, and image size but at first keep the settings as Automatic.

Although envira gallery lite doesn't include many features you have to purchase their pro version for more features.

Next, how to display our Gallery properly