Bring the statue and broken piece inside (You can skip this step if you live in a very dry climate).
Clean off any dirt and debris from the statue and the broken piece with a damp cloth.
Allow all of the cement to completely dry. It is essential that there is no moisture present in the cement, or the epoxy will not reach its full strength.
Mix a two-part cement epoxy on a paper plate. Some epoxies come with mixing nozzles that do the work for you. You can apply such epoxies directly to the broken pieces of the statue.
Spread the epoxy on both sides of the break with a small brush and fit the pieces back together. If you are using a fast-setting epoxy (5 to 15 minutes), hold the piece in place until it sets. This is tedious but will ensure the best possible repair as you can visually ensure that the pieces line up perfectly. If the epoxy takes longer to dry, fix the pieces together with duct tape until the epoxy cures.
Allow the epoxy to fully cure for 24 hours before returning the statue to its garden.