Go to View > Media > Browser. Navigate to the project you want to import then click the Import button at the bottom of the browser and make your selections. It's pretty intuitive but have a quick look at that section of the manual. You will like this feature - a lot.
How do I combine two projects?
Touch and hold your finger onto one of the projects you would like to merge. A purple frame around the project will appear and you can drag and then drop the project onto the other project you're merging. To merge more than two projects simply touch and hold, then lift your finger when the purple frame appears.
How do I copy from one logic project to another?
Choose File→Project Settings→Import Project Settings. A dialog asks you to find the project from which you want to import settings. Select the project, choose Import, and the window shown appears, displaying the settings you can import into your project. Select the project settings you want to copy and click Import.