The rule
A package belongs to the client who holds it. Two different clients cannot use the same package at checkout, so a client cannot pass their pack to someone else, and they cannot use their own pack to book another person in.

What to do if someone else needs one
Give that person their own package. Go to Clients in the left side menu, click the client’s name, open the Packages tab and click Add package. Adding a package this way does not take payment, so the client is not charged. If you want them to pay, let them buy it themselves at class checkout or from the Packages tab on your calendar widget. See Manually add, edit, cancel or pause a package and How clients purchase packages.

Gift cards are different
A gift card can be bought for someone else. The buyer gets a code by email and forwards it to the person they are buying for, who redeems it at checkout. That is a separate purchase for that person, not shared access to an existing package. See How to Create and Use Gift Cards.

If your case is unusual and you are not sure how to handle it, please email hello@classfit.com.