Install the Free Version
The free version of the themes can be found in the official WordPress repository.
Install Through WordPress Admin
Follow the instructions here: https://codex.wordpress.org/Using_Themes#Adding_New_Themes
Go to the theme page and then click Download.
After you have obtained the .zip file, go to your Dashboard > Appearance > Themes, and click on Add New at the top of the screen. On the next page, click on the Upload New Theme button, and upload the .zip file that contains the Elara files. Make sure to activate the theme afterwards.
For more information on adding new themes, go to https://codex.wordpress.org/Using_Themes#Get_New_Themes