2) Then once the first step is done, download this file and place it into your Unity Project as shown below. This will allow you to build your asset bundle file.
3) Add your stuff to the asset bundle as shown below.
4) Once you have everything in your assetbundle, build it by right clicking anywhere and clicking on Build AssetBundles as shown below.
5) If your assetbundle has succeeded building you should be able to find it in Assets/AssetBundles; Once you found it, copy it into your mod project folder where your .cs files and your modinfo.json file are located as shown below.
6 ) You can now put this file (only the .assets) with your plugin in your plugin folder near your plugininfo.json file.