I want to build a Wireshark packet dissector of my own and followed the procedure given at https://www.wireshark.org/docs/wsdg_html_chunked/ChDissectAdd.html .
However, I do not understand how to compile my dissector and place the dll in the plugins folder. I followed this guide https://www.sewio.net/open-sniffer/develop/how-to-compile-your-wireshark-dissector/ till step 2. But couldn't understand what to do at step 3.
I tried running nmake but it shows no such cmd command. I am using the Wireshark installation for Windows.
How can I compile my dissector and run it? Also is it necessary to build Wireshark from Source code in order to run custom packet dissectors?
First, since you're working on the Windows platform, you should be sure to read and follow very carefully the official Win32/64 Step-by-Step Guide section of the Wireshark Developer's Guide.
Second, if you're building a plugin, you should be sure to carefully read the README.plugins file.
You will need to compile the Wireshark sources if you're building a dissector written as a C plugin or builtin, but you won't need to build the Wireshark sources if you write your dissector as a Lua plugin. If you're interested in Lua, you might start at the Wireshark Lua wiki page.
There's also another less well-known method of building a dissector using wsgd. I have no experience with wsgd, but for an introduction to all 3 methods, you may wish to review Graham Bloice's presentation from Sharkfest '15 titled, "Wireshark Dissectors - 3 ways to eat bytes".