Kindly find the below step of bulk uploading:

In the product list page, you can see the export CSV option. Click on that and you will receive CSV file on your registered email ID.
Kindly add more product on that CSV and click on import from the product list page in the admin.
You can not update Images from the CSV file. For that, we have integrated Dropbox.
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Dropbox Steps:

 1) Login into dropbox

2) Go to “https://www.dropbox.com/developers/apps” and create a new dropbox app.   

 - In the first step choose “DropBox API” option

- In the 2nd step choose “App folder” option   

 - In the 3rd step give a name to this app    

- Click on Create app. This will create a folder(Apps —> “App name”) automatically. This folder is called an App folder. Integrated API will have access to only this folder.    

- On app detail page you will find a button to generate an access token. Generate access token and configure the same in our dropbox app(Apps and integrations —> Inventory —> DropBox)

3) To add images to a product, create a new folder under app folder with name “product SKU” and add images to it. To add priority to images, you need to sort the images in alphabetical/Numerical order. (Ex: 1.png, 2.png and so on)

4) Import product CSV. Max 5 images can be added to a product via DropBox. If the product is already having images then no changes will be done to its images.