You can save an image with changes pre-loaded. This is suitable for changes you want to share with other users of that image, and for code which takes some time to load. It cannot be used to alter settings which the system makes automatically on startup.
Saving a LispWorks image describes how to do this.
You can also load changes each time you start LispWorks. This is suitable for code which loads quickly. For changes only you want to see, put the code in your personal initialization file. For changes to share with other users at your site, put the code in your site initialization file.
Initialization files describes these initialization files.
The remainder of this chapter describes some customizations, all of which can can be saved in an image or placed in an initialization file, as needed. You can use both techniques: stable code including patches is saved in the image, while experimental or fast-loading code is loaded via the initialization file.
LispWorks User Guide and Reference Manual - 13 Feb 2015