In the main search bar of your Bitrix24 account, you are shown the search results in the six categories - Employees, Groups, menu items and subitems, CRM elements (leads, deals, contacts, companies) and files stored on the Bitrix24.Drive:
If you need to search in another Bitrix24 section, you can do that by scrolling down to the other sections lists and selecting the needed section.
Once you select the needed section, click its name, and you'll be taken to the corresponding section. Words or parts of words you have entered when searching via the main search bar are already entered into the selected section search bar.
It works the same way with searching for the information you need in any section - Activity Stream, Tasks, CRM, Calendars, Workflows, etc.
Next, you can apply filters to the information found to make the search results more precise.