Model or Aquire Objects

Create your own objects or Buy or get objects

1. Make your own objects. Learn how to model objects or scan them in. This means learning how to design. Use lots of reference images to help you. Use Iterations of a simple sketch, and then refine the one you like best.   Quickly adding multiple ideas are Paramount.  Chip Walters describes how important this is to Designing a Heads up display.
2. Buy Objects This is a great time saver. You still need to make a scene, but sometimes you can just drag and drop a pre-made object to save time. 
3. Get free objects There are some very high quality free objects you can find. Very good to learn shaders and an object is rigged. Save materials to the Materials library.  (Materials Library is a free plugin that you turn on in the blender preferences section under add ons. Until Blender implements it's asset management in Blender 3, Material nodes helps manage Textures)

Blendswap.com is an awesome resource for BLender users.   ALso you can use them in unreal if you export them out of blender as an fbx object.