doc: improve description/example for DPDK

Author: cejkato2

README.md

@@ -12,7 +12,7 @@ This application creates biflows from packet input and exports them to output in
 - [nemea](http://github.com/CESNET/Nemea-Framework) when compiling with unirec output plugin (`--with-nemea` parameter)
 - cloned submodule with googletest framework to enabled optional tests (`--with-gtest` parameter)
 
-To use DPDK interfaces, make sure you have DPDK libraries installed and set the `PKG_CONFIG_PATH` environment variable if necessary. You can obtain latest DPDK at http://core.dpdk.org/download/ (`--with-dpdk` parameter)
+To compile DPDK interfaces, make sure you have DPDK libraries (and development files) installed and set the `PKG_CONFIG_PATH` environment variable if necessary. You can obtain the latest DPDK at http://core.dpdk.org/download/ Use `--with-dpdk` parameter of the `configure` script to enable it.
 
 ## Build & Installation
 
@@ -149,7 +149,7 @@ Here are the examples of various plugins usage:
 # Read packets using DPDK input interface, enable plugins for basic statistics, http and tls, output to IPFIX on a local machine
 # Note that parameters for the ipfixprobe application go AFTER the '--'. Parameters before are passed into the DPDK EAL
 # The application will run on a core 0 as defined with EAL parameter -c using mask 0x1
-./ipfixprobe -c 0x1 -- -i "dpdk;p=0" -p http "-p" bstats -p tls -o "ipfix;h=127.0.0.1"
+For example: `./ipfixprobe -c 0x1 -a  "<[domain:]bus:devid.func>" -- -i "dpdk;p=0" -p http "-p" bstats -p tls -o "ipfix;h=127.0.0.1"`, where correct values for `-c` and `-a` must be specified.
 ```
 
 ## Extension