How can I search in the vi editor?

To search down through the document, use /[search string]

So you type "slash" and then the text you want. Hit the n key to move to the next result.

If you use a ? instead of /, you can search up through the document, instead of down.  Note that the search begins where your cursor is.

Also note that if you use the "N" you can find the next match in the opposite direction that you searched.