Please let me know how to activate IE window when there are multiple IE windows or multiple IE tabs.
If you have multiple IE pages, you can make your robot choose to work on one of them by using Attach Browser Activty and indicating the inside of the page where you want your robot to operate, you then drop the other activities in the do section of the first attach.
Many of UiPath’s activities activate the element by default before operating on it. This means that even if you have multiple browsers open, the activities themselves will find the browser that contains the element (because this information is usually in the selector given to the activity).
However if for some reason (there can be many reasons for this from my experience), the activity is not able to find the browser, you can use the Activate Activity to bring the browser to the foreground before operating on it.