1. Download SharePoint Online Management Shell (x86)

2. Download BulkUploadSharePointCSOM.zip. And move the BulkUploadSharePointCSOM.ps1 file in it directly to the root directory of your C drive.

3. Open SharePoint Online Management Shell.

Run: cd C:/

Run: Set-ExecutionPolicy -Scope Process -ExecutionPolicy Bypass, then choose Y

Run: .\BulkUploadSharePointCSOM.ps1 -UserName “*** Email address is removed for privacy ***” -Password “xxx” -SiteURL “https://MyO365Site.sharepoint.com” -DocLibName “Documents” -Folder “C:\UploadFile” -O365 $True

Note: Please replace the value above based on your specific requirement.

(UserName: Your Office 365 account name; Folder: The path of the folder you want to sync to Teamsite)

Then, wait until all the files are synced.