There is no Spot Light in Octane by default, but there are ways to do it. Now we will show you step by step how to do the simplest "Spot Light". Of course, this example does not include the complex features that may be in a spotlight. You need to write Expresso for this. Writing a script or Expresso is not within the scope of this manual, so we will keep our explanations at a basic level. However, there are both free and commercial products on the web regarding this subject.

You can download the example scene from here.  

1- Create a scene or download and open the scene from the link above that we provided to you. Once you've created the scene (or open), create a light by selecting Lights / Octane Area Light from the Live Viewer menu. Place this light somewhere on top of your subject and turn the "Z" axis towards the object.

2- Select the light you created from the object manager and select Cinema4D Tags / Target with the right mouse button. Then go to the "Target" Tag and drag and drop the desired object into the "Target Object" field. This option is for locking the light to a fixed point when you move it. It also makes navigating easier when you have PSR from Viewport.

3- From the Object Manager, select the light and go to the "Details" tab. Change "Area Shape" to Disc here.  

4- Now select Octane Light Tag. Here we will create a spotlight by defining a procedural texture in the "Distribution" section. For this, define the Octane "Gradient" for the texture channel of the Distribution (you can also define the native Cinema 4D gradient if you want). Change the options as you see in the picture below.  

5- And your Octane spotlight is ready. As you can see, we created spotlight easily with the gradient texture we defined in Distribution channel. If the above texture setup is complicated, you can use it in any alpha image texture. In this case you will select the "Image Texture" node instead of the gradient. You can change the brightness of the spotlight you see in the picture below by using power from Light settings. Or you can select the light from the object manager and play with "Outer Radius" from the details tab. If you want to change the spotlight's size, go to the gradient's sinewave options and scale with the texture transform. Likewise, you can change the edge softness of the spot by playing with the position of the "gradient" colors. The reason for our procedural texture assignment here is that it gives us more control. When we assigned an image texture, it will not have that much control. If you know how to write expresso, you can set all these options and more. It is also possible to make it more user friendly user interface.