In the second level of the first pack, there are single-block platforms. The last platform has the portal to enter.
Jump up and then move right until you are above the next platform. Continue until you reach the portal.
Obviously, if you do not land on the platforms, you will fall off and die.
"If you fall off, you die! Don't worry, you'll respawn."
"If you find a level too difficult, press the 'delete' key to go back to the menu."