I am unable to get Paypal chain to work on Marketplace

I have tried over a couple of days to get the following to work with no success:

paypal express

paypal chained

USPS shipping on Marketpress

I would like for you to go into my site:

I can provide the login details

my site is:

http://sdmerchants.com

I had the ProSites enable network wise for multisites but was also unable to get the paypal express to work for the payments so I disabled it in order to at least try to get the marketpress working.

I have watched videos and read all i can but now have reached the point where I need help please.

Thank you

Cheri Faline