AxCrypt does not work by starting a separate program, instead it is fully integrated into the Windows Explorer - the part of Windows where you browse your folders and files.
You may always right-click files and folders in Windows Explorer, bringing up the context menu. This is where AxCrypt is invoked, from it's own sub-menu.
The context menu is named after the intention to vary the options depending on the context where it is shown, AxCrypt follows this convention thus varying the available options depending on the context. If you're not seeing an operation, it's likely because it's not meaningful in that context, for example you will not see the decrypt option when right-clicking a file that is not encrypted since that would not make sense.
There are also some operations available from the program Start-menu, under the AxCrypt heading.
Always start by selecting one or more files or folders that you'd like to operate on. Some operations are not applied to specific files or folders, but you still need to right-click something to bring up the AxCrypt menu.
To open files for viewing or editing, just double-click them as you normally would.