To add HTML or Custom Code to a lesson in your course is easy.

First, go to 'Courses' then click the 'Course' you want to add the custom code to.

Next, go to 'Curriculum' > 'Add Lesson' in the section (eg. 'Other Media' ).

Enter 'Lesson Name' & 'Save Changes'.

Next, select the 'Custom Code' in 'Add Content'.

This will open up 'Add Custom HTML Code' window. Enter the 'Custom Code' and click 'Save'.

Once the custom code is added it will appear here:

Go to 'Preview' to view your 'Course Curriculum as a Student'.

Then, navigate to 'Other Media' and select 'HTML or Custom Code' you just added.

If you are a developer, you may want to utilize the custom code feature to embed code from different apps or services. Zenler's custom code block allows for greater flexibility and customization in your course creation.

NOTE: If you are a developer and proficient in HTML and custom code, this is a suitable option for you. However, if you are unsure about custom code or lack experience using it, it is advisable to avoid it.