Most of the sign-in from strings are editable within the theme options in the sign-in module of your page builder. Please, check out this doc for more details Sign-in form extension. Some of the strings marked with green boxes can't be translated within the theme settings, but they can be translated with help of the "Loco Translate" plugin.
Now let us show how to translate/edit other strings via the "Loco Translate" plugin. First of all, please install and activate the plugin from the WordPress repository.
Once it is installed and activated, go to the Loco Translate settings and follow the next steps:
1. Loco translate > Themes
2. Choose the Olympus theme:
3. Sign in Form extension and add a new language:
Note: if you just need to edit the text strings and not translate into another language, any way you need to add English language and after that begin to change the text. For example:
4. Begin searching for a needed string and edit the text in the translation field:
5. After that, hit the "save" button.
If you need to translate the string into another language, simply choose the needed language from the drop-down list and begin translating strings:
Note: Translation will be applied automatically if you have installed WordPress in the corresponding language.