Are there spaces in the name of the files or folders you are trying to access? If so, then you either need to "escape" the spaces
using back slashes "\" or you need to enclose the path in double quotes.
For example:
ls ~/folder\ with\ spaces
ls ~/"folder with spaces"
ls "~/folder with spaces"
An easier way is to press the Tab key to auto fill the unique part of the path. For example using the above as an example start by typing
ls ~/fo
Now press the Tab key which will fill in the rest of the name automatically as long as there are no other items in the folder beginning with "fo". If the Tab key does not autofill in any more of the name, then press the Tab key a second time which should provide a list of possible choices. If there are other items within the folder with "fo" in the name, then you need to type more of the name so that the Tab auto completion can determine which items is desired. If you don't get a list of choices or it does not auto complete, then either you have mis-typed something, or you don't have permission to read the items in the folder, or the command you are using does not allow auto completion. FYI, auto completion does not work when using double quotes in the path.