These instructions assume you have not previously created a mod folder. Here's how to do that:
Create a folder called custom in your cstrike folder.
Inside custom, create a new folder with the name of your choice.
Inside said folder, create a folder called maps.
Put the .nav file inside this maps folder.
Important! Putting this .nav file in the regular maps folder and replacing the existing de_dust2.nav will result in absolutely nothing, which is why this stand-alone .nav has to be installed as a mod. Welcome to my most controversial submission yet.
This .nav file tweaks a number of smaller bugs and adds more paths to the bots' navigation for the beloved de_dust2. In general --and in theory--, the bots should be less stupid now.
However, if you encounter any bugs, make sure to point them out, so I may get around fixing them.