ImpressCMS Modules are uploaded and stored in the the "modules" folder.
When you install ImpressCMS, the modules folder contains one module: 'system'.
You should copy other modules into the same directory as this one, so the modules folder should look like this:
Some modules include more than one folder in the pack. Which one should be copied to the modules folder?
It is always best to follow the module authors instructions, however generally:
If there are additional steps aside from uploading the physical module folder, they will be identified in the module authors installation guide.
Now, after you have uploaded the module folder, and all (if any) of the additional requirements for installation, you will need to physically install the module.
Copying/Uploading is not the same as installing. Installation is the process you must undergo through the ImpressCMS control panel.
Go to ImpressCMS control panel > modules. If you just copied one or more modules, there should be two lists.
Click on the install button, located next to each module row. You can hover over the icons to view a tool tip if you cannot clearly identify which icon to use.
If nothing goes wrong, your module is now ready to use. Each module should then be configured according to the documentation provided by the module author.
In the event that you experience errors, or have difficulty installing a third party module into ImpressCMS, it is best to contact the module author for the fastest possible solution. Though the community forums here at impressCMS.org are available for support questions as well.
About Modules with Trust Path
A new generation of modules based on the concept D3 and D4 is emerging. The modules will behave differently.
Usually this type of module contains its code in two places.
The first and equally important should be placed in the Path of Trust from your website and in general will be outside your web root.
The second step should be done as a normal module, and will be sent to the modules directory as the others.
Advantages and disadvantages of this technology
The great advantage of the modules that use this technology.
Conclusion (weight on scale):
The approach of the modules of this generation tend to be more secure by nature. The advantages outweigh the disadvantages and you will be happy to use this technology after learning how to do this correctly.
Tip: Whenever you use a module with Trust Path you should see very clearly the developer documentation.You have to follow this specification.