To open a project, choose the menu item File->Open Project …. Select the project file (*.prj) in the dialog and click OK.
If the project has recently been opened, then you will find it listed in the menu File->Recent Projects. Choose the project file from the list, and the project will be opened.
As soon as a project is opened, Anjuta will enter Project mode.
To save the current project, choose the menu item File->Save Project or click on the Save Project button on the Extended toolbar. When a project is saved, only the files that need to be updated are actually written to disk, to avoid breaking any unnecessary dependencies.
Any build files that are flagged Disable Overwriting in the project configuration will also not be touched.