If you are using an earlier version of Stellarium, you can follow this procedure to install a landscape package: Landscape packages created without this feature in mind may contain other files, such as alternative textures in different sizes. Note that while this makes installing landscapes easier, it may also cause you to overlook what else is included in the ZIP archive. It also lists the user-installed landscapes and allows you to remove them.

Open the 'Sky and viewing options' window by clicking on the appropriate button in the left button bar (or press the F4 key).If you have Stellarium 0.10.6 or later version, you can use the 'Add/remove landscapes' feature to install landscapes automatically: zip file for a landscape from this page, you need to install it in Stellarium.