There are four common ways to make fruit-flavored ganaches:

1. Use the zest of the fruit Zest the fruit (works best for cirtus) and place the zest in the cream as it is brought to a simmer. Strain out the zest and use the cream.
2. Use reduced juice Fruit juice from almost any fruit may be used as a liquid flavoring in ganache. The fruit juice should be heated until it is about half of its original weight. The reduced fruit juice can often be used as a 1:1 (depending on the type of juice you might want to increase the juice slightly) substitute in recipes that call for a liqueur. Like a liqueur, it is stirred in slowly (a little bit at a time) after the ganache has been mixed together.
3. Use a fruit-flavored liqueur A third option is to find a liqueur with the correct flavor. It should be added slowly after the chocolate and cream have combined and formed a smooth ganache, but before the ganache has cooled.
4. Use an extract or flavoring oil You can also use an extract or flavoring oil. Extracts should be treated like liqueurs. Flavoring oils (such as these) should be added in VERY small quantities after the ganache has become smooth.

The first option may be combined with the 2nd or 3rd. If you choose to combine the 2nd and 3rd options you would have to use half of each, because doubling the liquid in a ganache will either change the consistency or cause it to break.