Dear Sadman Sakib_106,
Good day! Thank you for posting to Microsoft Community. We are happy to assist you.
As per the description you have shared, we understand that you want to import ics in outlook web or mac app.
To import your .ics file in your Outlook for mac, please kindly Go to Calendar -->In the Finder, locate the .ics file, and drag the .ics file to the Outlook Calendar grid or list -->Select your account where you want to import -->Click on Importin the Add Event menu. You can refer to the screenshot below.
For additional information, you can refer to Import iCal items into Outlook for Mac - Microsoft Support.
Besides, to import iCal into the Outlook on the web, please kindly Open your browser -->sign into your Outlook on the web account -->Select Calendar-->In the navigation pane, select Add calendar -->Select Upload from file -->Select Browse,choose an .ics file, and select Open -->SelectImport. You can refer to the screenshot below.
We look forward to you update. Please feel free to let me know if there are any questions. We will keep assisting you based on the information you provide. We sincerely appreciate your patience and cooperation.
Thanks for your precious time. Have a nice day.
Sincerely,
Libeamlak | Microsoft Community Moderator