The theme included a translatable .pot file. You can translate the theme in two ways:
1. Translate the .POT language file
If you edit the .POT file with a program like PoEdit add a new translation. After setting up the language you can translate each text string to your own language.
When you're done export a .po and .mo file which you need to upload in the language folder of the theme (theme-folder/language/). For more information please see this link
2. Translate with the Loco Translate plugin
With the Loco Translate plugin you can translate the theme inside your WordPress installation.
Please install and activate the Loco Translate plugin. Then follow these steps below:
1. Please navigate to Loco Translate -> Themes
2. Click on the correct theme name in the list
3. Click on the 'New Language' link
4. Set your language from the dropdown field
5. Set 'Choose a location' to Custom and press the Start Translating button
5. Type the word you want to translate in the search box and click on it when it appear in the list below
6. Write your translation in the bottom textarea (the translation textarea)
7. Save the settings
You can read this tutorial for more information how to set-up a new translation (screenshots included)