An application for the HSE 'GP Visit Card' for under 6 yr old and over 70 yr old patients of the Corbally Clinic can be done online through the HSE here 
Alternatively you can find it at www.gpvisitcard.ie 

For Corbally Clinic the scheme is under the name of "Dr. Mary Gray" which you choose from a list of GP names on the site. 
The website explains what is needed to register - principally your PPS number. For children the PPS number of the parent/guardian and the PPS number of the child are needed. (Unless the child is under 2 months of age in which case the PPS number is not needed if you do not have it yet).

If you do not have the PPS number we may have it on file as it is needed for certain state schemes so contact us. Alternatively you can contact the Department of Social and Family Affairs as below: 

If you have a query regarding your PPS Number please contact:
Client Identity Services,
Department of Social Protection,
Social Welfare Services,
Shannon Lodge,
Carrick-on-Shannon,
County Leitrim
Telephone: Lo Call 1890 927999
Email: cis@welfare.ie

If your child already has a current medical card you do not need to do anything.