You need an insurable interest in someone in order to insure that person's life for life insurance.
However, you also need their consent to purchase life insurance on them.
With insurable interest and the person's consent, the process is simple.
You can apply for a life insurance policy through a life insurance agent, or online through a life insurance website.
The cost of the life insurance policy will depend on your husband's rating (health) and age.
Assuming your husband has a reasonable occupation, and his health rating is fair, your cost will then depend upon the amount and type of life insurance coverage you wish to purchase on your husband.
Here's how you may apply for term life insurance online for your husband.