The stock Like/Tweet button switches are located in the General Display Settings (CP -> Display Settings -> General -> Primary Tab -> Topic & Post Page Settings).

Note however, that they're horrible; and in more recent builds we've begun using Shareaholic, which has an ID field in the same place as above, however you'll also need the javascript inclusion code from Shareaholic which will need to be added to the "HTML Includes" tab in the same area (the field is called "Shareaholic 'Setup Code'"). See the UBBWiki entry Shareaholic.

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