README: update the main readme document

Author: Lukas955

README.rst

@@ -31,12 +31,12 @@ network interface and a port. Multiple instances of these plugins can run concur
 **Intermediate plugins** - modify, enrich and filter flow records.
 
 - `anonymization <src/plugins/intermediate/anonymization/>`_ - anonymize IP addresses
-  (in flow records) with Crypto-PAn algorithm.
+  (in flow records) with Crypto-PAn algorithm
 
 **Output plugins** - store or forward your flows.
 
 - `JSON <src/plugins/output/json>`_ - convert flow records to JSON and send/store them
-- `dummy <src/plugins/output/dummy>`_ - simple module example,
+- `dummy <src/plugins/output/dummy>`_ - simple module example
 - `lnfstore <extra_plugins/output/lnfstore>`_ (*) - store all flows in nfdump compatible
   format for long-term preservation
 
@@ -85,41 +85,53 @@ Finally, build and install the collector:
     $ make
     # make install
 
-How to configure
-----------------
+How to configure and start IPFIXcol
+-----------------------------------
 
-TODO: Prepared configurations
-
-TODO: example configuration files
-
-TODO: description of information elements are
+Before you can start IPFIXcol, you have to prepare a configuration file. The file describes how
+IPFIXcol is configured at startup, which plugins are used and, for example, where flow data will
+be stored. The structure of the configuration is described
+`here <doc/sphinx/configuration.rst>`_. Several configuration examples that demonstrate features
+of the collector are given in the section
+"`Example configuration files <doc/sphinx/configuration.rst#example-configuration-files>`_".
 
+Coming soon
+-----------
+- NetFlow v5/v9 support
+- Runtime reconfiguration (improved compared to the previous generation)
+- RPM/DEB packages
+- Support for structured data types (lists, etc.)
 
 FAQ
 --------------
 
 Do you have any troubles? Unable to build and run the collector? *Feel free to submit a new issue.*
 
 We are open to new ideas! For example, are you missing a specific plugin that could
-be useful also for other users? Please, share your experience and thoughts.
+be useful also for other users? Please, share your experiences and thoughts.
 
 ----
 
-:Q: How to...? UDP or TCP
-:A: You should...
-
-:Q: How to...? UDP and no records
-:A: You should...
+:Q: My exporter sends flow data over UDP, however, the IPFIXcol doesn't process/store any data
+    immediately after start.
+:A: This is normal behaviour caused by UDP transport protocol. It may take up few minutes until
+    the first record is processed based on template refresh interval on the exporter.
+    For more information, see documentation of `UDP <src/plugins/input/udp>`_ plugin.
 
 :Q: How can I add more IPFIX fields into records?
 :A: The collector receives flow records captured and prepared by an exporter. IPFIX is an
     unidirectional protocol which means that the collector is not able to instruct the exporter
     what to measure or how to behave. If you want to enhance your records, please, check
     configuration of your exporter.
 
-Coming soon
------------
-- NetFlow v5/v9 support
-- Runtime reconfiguration (improved compared to the previous generation)
-- RPM/DEB packages
-- Support for structured data types (lists, etc.)
+:Q: After *manual build and installation* the collector is unable to start and a message similar to
+    ``error while loading shared libraries: libfds.so.0: cannot open shared object file: No such file or directory``
+    is given.
+:A: Make sure that ``libfds`` is installed properly and your system is able to locate it.
+    Some systems (e.g. RHEL/CentOS/Fedora) for historical reason doesn't search for shared libraries
+    in the default installation directory where the ``libfds`` is installed. You can permanently
+    include this directory. For example, if the library is located in ``/usr/local/lib64``, use
+    as administrator "``echo "/usr/local/lib64" > /etc/ld.so.conf.d/local64.conf && ldconfig``"
+    or temporarily change an environment variable
+    "``export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/lib64/``"
+