In order to install MarvelClient on your very first client, you may either include it in a rollout to multiple clients or proceed with a manual installation as follows: 

• In the Configuration database, click on Administration > DLL Updates and open the document for the respective operating system (newest at the top).
• Save the attachment as mc.dll/mc.dylib/mc.so into EITHER your Lotus Notes Program OR your Lotus Notes Data directory.
  Note that on Citrix the Program directory is highly recommended, however not required.

• In notes.ini, please search for an entry “EXTMGR_ADDINS=”
• If such an entry already exists, please add “mc.dll”, “mc.so” or “mc.dylib” accordingly – without quotes, with comma separation – for example:
  EXTMGR_ADDINS=EntryOne,EntryTwo,mc.dll
• If such an entry does not exist yet, add a respective new entry/line to your notes.ini:
  EXTMGR_ADDINS=mc.dll
  
  Note that there must not be more than one “EXTMGR_ADDINS” line in notes.ini, as only the very first such line is relevant, any others are ignored by IBM Notes.
  Also note that when adding a new line to notes.ini, the very last line of notes.ini must be an empty line (this has nothing to do with MarvelClient).
• Add another new line/entry to notes.ini as follows:
  MC_DB=Servername!!Directory\FilenameOfYourConfigurationDatabase.nsf
  (Adjust Servername, Directory and Filename as needed)
  Server and filepath are separated with a double exclamation mark (!!). Server and filepath must correspond to where you chose to install the MarvelClient Configuration database.
  Please note, that “MC_DB” supports the placeholder “%notes_homeserver%” which is dynamically replaced at run-time with the then current end-user’s mailserver, for example:
  MC_DB=%notes_homeserver%!!panagenda\panagenda.nsf

See Also
Performing a manual install of panagenda MarvelClient
Creating the MarvelClient databases on the first IBM Domino server