If you're using the Find dialog, you can use the 'Highlight all matches' checkbox option.
If you're searching on the command line (like you should, Mr Vim User), then you can use the # option (mark all) in conjunction with the * (for find all). So to look for and highlight all instances of searchfor in the current editor window, on the command line type
/searchfor/*#
You may also like the highlight matching for incremental search. Go to Tools > Options > General > Search, and check the 'Incremental Search highlighting' option.