Website Access

I've created a domain pointer for our patient portal which points to an ip address on the internet.   However when the patient navigates to the website they have to add additional information to the address to get there.  How can I solve this  ....

They have to enter https://portal.companyname.com/abcportal   ,   I'd like them to only have to enter https://portal.companyname.com  and it directs them to the correct place.

Thanks .....