First, don't call "mario portal 1.6", simply "mari0 1.6", you'll say "why?", that name is a bit confusing as there is a mod with the same name (although it has a new) is known more for that. (Mario+Portal or Mario HEC)
Second, to put or create a mappack open Mari0 1.6, go in the menu to select mappack, go down and select the option "New mappack" to create a new mappack, edit the tiles, put entites, test, etc. and save this to play the time you want.
Third, If you want publish your mappack, in the select mappack menu press "m" to open the mappack folder, go to "mappacks" folder and search your mappack you make, rename this with the name that you like, convert this in a zip or rar (WinRar, WinZip, 7Zip, etc.) and upload in a download page (Mediafire, Dropbox, etc.)
This thread help better:viewtopic.php?f=12&t=1642
And please, don't make a entire thread for only ask for a single thing, It's against the rules.