I'm working from memory; its been 40 years since I did one! I presume they are the same today. There will be two heavy wire rails tha guide the front panel. These get screwed to the back of the end posts that go in front. Once you get them in place, the rest should be fairly obvious, and consists of fastening the rear fixed panel to the end frames.
Then you lay the spring assembly in the bottom; there should be swivel hooks on the spring frame that drop into some sort of brackets. There will be a heavy wire bail on the front of the spring frame that releases the front panel.
After that, set the mattress in place.