If the last thread guide is on the right, put the thread in from the right. If the last thread guide is on the left, put the thread in from the left.
I have two machines that have very different threading from the spool to the needle. One is a Delta Rotary and the other is the Eldridge Two Spool. The thread comes from the spool, over the edge of the face plate, makes a complete right turn around the tension mechanism, down to a thread guide, up to the thread take up lever, crosses over it self again to the next thread guide and then down to the needle. I would never have figured that out without the manual.