The search screen has a box to type a word or phrase to look for.

This will look for any of the words in topic titles and messages. To search for an exact phrase type the phrase in quotes. Example:
Selecting the advanced search link gives you more options.

Tip: To search messages by all authors, leave the '*' in the Author box. If you don't know the exact name of the author, try using the first letter + *, eg 'A*' - this will search for all mesages by authors with a username beginning with that letter.

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