merging 2 user profiles on same Mac air

The best solution is to not be in this position. In other words, when you first set up your Mac you should use Setup Assistant which will create a Mac account for you and pull the data from your other computer into that account. But now that you are here...

Like Windows, the Mac is a multi-user operating system and you are locked out of all accounts but yours. But inside the Users folder you'll find a folder labeled Shared. As the name implies, anything in this folder is accessible to everyone. You can put files into this folder and everyone will be able to access them. There's one caveat - the ownership doesn't change but you can change the ownership. So...

Log into the account you want to move data from. Create a folder inside Shared - call it anything you like - Moving is good. Move the folders/data you want to put into the other account into that folder. Don't drag loose files into Shared, make sure everything goes into that folder you created, it will make changing ownership easier. Once you've put everything into the folder, select it and go to the File menu of Finder and select Get Info.

Click on the lock in the bottom right corner and enter the User Name and Password of your admin account. Then click on the plus sign and select the user name of the account you are moving into. It will appear in the list. Click in the privilege column next to that user name and select Read & Right. Then click on the gear next to the minus sign and select Apply to Enclosed items. Click on the lock to close it. Now log out and log into the account you are moving into. You can now move the files where you want them.