I am trying to access LS from internet in order to manage my surveys.
url:
www.mysurvey.com/admin
Is there a parameter to activate in order to allow access to the admin console?
If you tried survey.domain.tld/admin
LimeSurvey should rewrite it to survey.domain.tld/index.php/admin (on Windows IIS it's different).
and then to survey.domain.tld/index.php/admin/authentication/sa/login
That works out of the box if settings of limesurvey and environment are correctly set.