Searching for datasets on HDX is done in two ways: by searching for terms that you type into the search bar found at the top of almost every page on HDX, and by filtering a list of search results.
Entering a search term causes HDX to look for matching terms in the titles, descriptions, locations and tags of a dataset. The resulting list of items can be further refined using the filter options on the left side of the search result. You can filter by location, tag, organisation, license and format as well as filtering for some special classes of datasets (like datasets with HXL tags or datasets with Quick Charts) in the 'featured' filters.