During the scheduling process, you will see the option to input a "Chat Price", and also to enable (or disable) donations. You can use any combination of free/paid and donation enabled chats.
The "Chat Price" is the price that a fan will have to pay prior to receiving a chat slot. You will have the option to have the chat be "Free", or charge a price by selecting "Paid" and entering in your desired price.
Donations are an optional feature. By toggling "Donations" to "On", the fan will be prompted after their chat with you that asks if they would like to support you by giving a donation!
This is completely optional for fans, but it allows them to show their additional support after they have a chance to speak with you!