Head to the sources page from the bottom of the left hand menu
Click Connect an Organisation at the top left of the Sources page.
This will bring up a page like the following in Xero where you can select the organisation you wish to connect.
Choose the organisation you wish to connect, and then click the blue "Allow Access" button. This will take you back into Mayday, and the software will finish connecting. This can take a few moments, so please be patient!