Please make sure that you have unzipped the theme package that you download on Theme Forest before upload it to your store. Otherwise, you will get the issue: zip does not contain a valid theme: missing template "layout/theme.liquid". Then please upload Theme_x.x.zip file to your store.
Note: "Theme" - it means name of your theme such as Kalles, Gecko, Unsen and Ocolus.

1. Import Demo
Step 1: Download and Extract File Zip
To import the demo, you need to download the full package on Theme Forest and extract the file zip.
Step 2: Find the "Theme Data" file
You will find the demo that you want in the Theme Data.
Step 3: Copy then paste files Setting_data_json and Index_json
You need to upload 2 files Settings_data_json and Index_json of the Demo that you want.
Notice: You must install Sublime Text (or other editor softwares) to your device in order to open index.json and settings_data.json. You can click here and choose the suitable Sublime Text version to install.
When you complete the import file, you need to active the theme with your license code.

2. Select the available demo in EComposer Library
Note: Kalles and Unsen's demo in EComposer is available. However, the Demo EComposer library is not yet fully available. We are currently in the process of updating it. Therefore, for any Demo that is not yet available, please use and import the theme through Shopify - Online Store - Themes.
2.1. Some FAQs about Unsen EComposer
I have theme of The4 installed and full features, why do I need theme for EComposer? Theme's The4 is of great quality, however EComposer was not developed to replace Theme's The4. It was made to fix Shopify editor problems, with Theme's The4 you can only customize everything the theme or Shopify allows but with Theme's The4 EComposer you are free to change the layout that you want.
When should I use Theme's The4 EComposer? When you have a high need to build landing pages or about, contact... at your discretion. You can absolutely use EComposer to create those pages.
I just want to use Theme's The4 is that possible? Absolutely, if your need is everything Theme's The4 has then just use it. Theme's The4 EComposer is only recommended when you have high customization needs, and want more advanced functions (like upsell extensions and high-quality layouts...). To use Theme's The4 EComposer, you are still required to installTheme's The4.
What is EComposer better than Shopify editor? It's pretty hard to explain it all here, you can try the demo at https://demo.ecomposer.app. Some outstanding powerful features can be mentioned such as a diverse library of libraries (you can combine them with Theme's The4), an extension store that allows you to have advanced features, a flexible drag-and-drop system, Various elements that allow you to build anything, the auto-save function allows you to avoid losing your work, easy to use custom fonts.....
2.2. Select the available templates from the EComposer library to use
Step 1: Upload Theme's The4 and activate the theme
Please follow the existing tutorial on activating the theme here.
Step 2: Install EComposer App
Go to the EComposer link from the Shopify app store and install it

Step 3: Go to EComposer app and enable App Block
Please follow this quick guide from EComposer team to understand this step.
Step 4: Select the available demo in the EComposer library
Please follow this video below: