Based on the Galleriffic gallery, Photospace takes advantage of the built in gallery features of WordPress.
Then simply use the WordPress admin to create a gallery and insert it in the page. You may need to adjust the size of the gallery to suit your theme in the settings.
Since WordPress 5 you need to embed the gallery using the classic editor.
Make a note of your settings as with the last major update, you will need re-save your settings.
The Photospace gallery plugin allows you to:
Via the options panel you can modify:
Some other features include:
See a demo here