Short Answer 
To disable the Research Pane in Excel, start by clicking the File tab and then selecting Options to open the Excel Options dialog. Go to the Add-Ins section, select COM Add-ins, uncheck the Research option, and confirm your changes by clicking OK.
Step 1: Access Excel Options
Begin by launching Microsoft Excel and navigating to the top left corner of the application. Click on the File tab, which will open a menu with various options related to your workbook.
Step 2: Navigate to Add-Ins
In the options menu, look for Options and click it to open the Excel Options dialog box. Within this dialog, find and select the Add-Ins section to view any add-ins currently enabled for your Excel application.
Step 3: Disable the Research Pane
Once you’ve selected the Add-Ins, locate the Manage box at the bottom of the dialog. Choose COM Add-ins from the dropdown menu and click Go. You will see a list of available add-ins; uncheck the box next to the Research option and click OK to confirm your changes and eliminate the research pop-up.