Navigate to the project (or projects) you want to export in the PS Touch project selection UI. Tap the export icon (5th icon from the top right) > Save to Gallery (Picture Roll if using iOS). Ensure that JPEG is selected as the file type and tap the project you want. Tap OK. Wait. Profit.
(You can use the "Share" option as well instead of Save to Gallery or Picture Roll if you want to share it. This will export the project for use in something like Twitter but note the associated app has to be installed.)