update installation instructions

docs/installation.md

 # Installation
 
-There are two options for using DNS Shotgun. You can either install the
-dependencies and use the scripts from the repository directly, or use a
-pre-built docker image.
-
-## Using script directly
-
-You can use the toolchain scripts directly from the git repository. You need to
-ensure you have the required dependencies installed. Also make sure to check
-out some tagged version, as the development happens in master branch.
-
-```
-$ git clone https://gitlab.nic.cz/knot/shotgun.git
-$ git checkout v20210203
-```
-
-### Dependencies
-
-When using the scripts directly, the following dependencies are needed. If you
-only wish to process shotgun JSON output (e.g. plot charts), then dnsjit isn't
-required.
-
-- [dnsjit](https://github.com/DNS-OARC/dnsjit): Can be installed from [DNS-OARC
-  repositories](https://dev.dns-oarc.net/packages/).
-- Python 3.6 or later
-- Python dependencies from [requirements.txt](https://gitlab.nic.cz/knot/shotgun/-/blob/master/requirements.txt)
-- (optional) tshark/wireshark for some PCAP pre-processing
+There are two options for using DNS Shotgun. You can either use a pre-built
+docker image, or install the dependencies, compile the dnssim module and use
+the scripts from the repository directly.
 
 ## Docker Image
 
@@ -51,3 +28,36 @@ $ docker run \
     registry.nic.cz/knot/shotgun:v20210203 \
     $COMMAND
 ```
+
+## Using scripts from sources
+
+You can use the toolchain scripts directly from the git repository. You need to
+ensure you have the required dependencies installed and the compile and install
+the dnssim module. Also make sure to check out some tagged version, as the
+development happens in master branch.
+
+```
+$ git clone https://gitlab.nic.cz/knot/shotgun.git
+$ git checkout v20210203
+$ cd shotgun/replay/dnssim
+$ ./autogen.sh
+$ ./configure
+$ make
+$ make install
+```
+
+### Dependencies
+
+When using the scripts directly, the following dependencies are needed.
+
+If you only wish to process shotgun JSON output (e.g. plot charts), then dnsjit
+and compiling the dnssim module isn't required.
+
+- [dnsjit 1.2+](https://github.com/DNS-OARC/dnsjit): Can be installed from [DNS-OARC
+  repositories](https://dev.dns-oarc.net/packages/).
+- libuv
+- libnghttp2
+
+- Python 3.6 or later
+- Python dependencies from [requirements.txt](https://gitlab.nic.cz/knot/shotgun/-/blob/master/requirements.txt)
+- (optional) tshark/wireshark for some PCAP pre-processing