A useful asset becomes part of a scene when its scale, placement and organization match the rest of the project. Start with those decisions before adjusting individual materials.
Append or Link
Use File → Append to copy objects or a collection from another .blend. The copied data belongs to the current file and can be edited independently. Link is useful when several scenes should refer to the same source: changes to the source can then be shared. Keep linked files in a predictable project directory.
Check dimensions
Select the main object and inspect Dimensions in the Item panel. Compare it with something familiar in the scene, such as a door or a human figure. A scale mismatch changes the way lighting, depth of field and simulation settings behave. Apply Scale when your modifiers or simulation require it, rather than applying every transform without a reason.
Place and organize
Move the asset’s collection into a clearly named group. Check the object origin before rotating or instancing it. For repeated objects, Alt+D shares mesh data; Shift+D makes an independent duplicate.
Keep the working scene readable
Hide alternative variants that are not used in the shot. Preserve the original downloaded file separately so that you can return to its initial materials and proportions later.