I started the migration assistant and after I seen it was going to take a few days to complete I canceled it. Now I seem to have over half my SDD taken up and I cant figure out where those files are and what I have deleted, the trashcan shows as still there with a little lock next to the files. I dont know what to do about this. First mac, and totally new to this.
I assume your account and all your data is still on the other machine you want to migrate from?
If it is, just create a new temporary admin account on the new machine then from that account delete the real account. This will erase all the data that is filling you drive now. Then from within the temp account run the Migration Assistant again using an ethernet connection if you can. This will bring in your account and data from the other machine.
Once the import is done login to your real account that was imported and if everything looks okay, delete the temp account.
You can also run Migration Assistant from an Time Machine backup of the old machine if you have that on an external disk.