Click on an announcement you are interested in. Check the date of the publication (some opportunities in Morocco might be already expired). If the announcement is still valid look for the ‘contact details’ section to extrapolate the contacts of the hosts. Send them an e-mail and wait for a reply.
Some of these opportunities are completely free (you receive free food and accommodation in exchange for voluntary work), others require a daily contribution fee for the food. Read the announcements carefully.