If you want to change who covers your fees, you'll want to go into your page's settings, which is accessible by the cog button from the Dashboard or the Page Editor.
Afterwards, select the fees tab show below:
If you'd like the attendee/purchaser to cover your fees, select Purchaser.
If you'd like to absorb the fees yourself, select You.
If you'd like to let the attendee/purchaser decide, select Optional.
Don't forget to update your page if it's already been published! That way your changes will reflect.