An edit permission must be given to a module for all users you want to have edit access.

Make your tests being the host or admin first to ensure you have those rights.

Also, it could depend of your container design, but in most cases you can locate the edit link of the text/html module by using the upper-left menu inside each module space

You post is bit confusing. You are talking about permissions to a file and then about the text/html

File permissions are managed using the file manager and you can set permissions based on DNN roles

I will suppose that you are talking about the text/html module:

What a module does with each permissions set depends on how that module was built. And in the case of text/html, you can set who can view the content a who can edit the content. Take note that this module does not allow to edit just a part of this content

But, you have the option to drop more than one text/html module onto any page, then you can set view or read permissions to each module (Maybe the top as view only and other with edit permissions)

Each module has its own set of properties for title, container, etc. One of these properties is the permissions set. You can access those properties by accessing the module settings through the menu located at the upper-left part of each module.

Now, I will ask to focus this specific forum to FCKeditor related stuff. You can always continue to ask using the corresponding forums and maybe I can continue to answer but keeping each post related to each forum