Do you mean to say you get the option to upgrade your Lightroom 4 Catalog to Lightroom CC?
If that is the case, choose to Create a New Catalog so that it can create a New Empty Catalog for you without carrying over old images.
Or, if it has already upgraded, go to File menu > New Catalog to create a new catalog.
You can use the menu command File->New Catalog; or simply tell Lightroom CC to not upgrade the Lightroom 4 catalog.
If I could provide some advice, normally the best procedure is to have all of your photos in a single catalog, rather than to start a new catalog at an arbitrary point in time when you purchase a newer version of Lightroom. One catalog has many advantages, including the ability to search and make use of all of your photos, and virtually no drawbacks. Multiple catalogs mean you cannot search and make use of some photos that are in your new catalog and some photos that are in your old catalog.