I think you misunderstood something about scripts.
All scripts are automatically imported into the engine when placed in the script editor, resulting them to be available at the same time.
Usually those scripts have different functions and are independent of each other - that's why they work by default.
Some scripts (like menu scripts) are intended to be linked to other scripts - they have instructions on how to create those links.
The only part where you might have problems is when one script creates a new scene and you want the functions of that scene changed to work like a different script - that requires reprogramming both scripts. This can be easy in some cases and difficult with other scripts.
So basically, the answer to your question depends on what those scripts are, it can't be answered generally for any script.
Give us the names of those two scripts, and tell us what you want combined, and then we can give you an answer.