When you say that you have started a new project, do you mean you have created a new catalog? If that is the case then please explain exactly what it is you want to do.
Yes New Catalog.
You don't have to create a new catalog every time you import, in fact, having more than one catalog is a bad idea.
And, as you've found out, you can't see the images from catalog 1 in catalog 2, unless you import them into that catalog as well.
Import everything in one catalog, and use keywords, ratings and collections to organize and find your photos.
To understand how Lightroom works, this article might be helpful - Lightroom basics