To open the Find/Replace dialog, click Edit > Find and Replace or press Ctrl+F.

"The Find/Replace dialog"

Even if you set Scope to be All, the search will only be performed from the current cursor position forward or backward depending on the Direction setting to the end or beginning of the file, unless you select the Wrap search checkbox.

Searching is case insensitive by default, but you can change this by selecting the Case sensitive checkbox.

Select the Regular expressions checkbox to use Java regular expressions in the Find field.