Hey there, @StellarVistaObservatory - great question! Firstly, check out our New User Guide - it’ll def prove helpful as you get used to the platform!
We have integrations with both Stripe and PayPal. You can connect your Stripe or PayPal account to Calendly to collect payments when your invitees schedule with you. If you don't use these services, you could add a custom link to your confirmation page that leads to your preferred payment provider. You could also customize your invitee notification emails to include that link!
At this time, when setting up payment collection, it is required that you enter an exact dollar amount. There is not currently a way to accept donations or chosen amounts via payment collection integrations. However, you could choose not to use our integrations and instead, include a note in the event type about following the payment link to pay what an invitee desires.
I hope this helps!