You need the head and bottom of the bed frame (top right corner), the two sides (bottom right side) and the two pieces of the base (top left).
Depending of my making of the bed, you might need four pins (I provide them so if you don't have any, you don't need them).
Assemble the sides to the top and bottom, inserting the square piece on the side of the frame between the two squares of the head and bottom.
If you don't have pins, the side of the bed frame should fit nicely as in the picture below.
If you have pins, make sure you match the numbers or letters.
Do the same at the four corners.
Fit the rectagles of the base in the frame, push them to the corners. It will keep the bed angles at 90°.
Insert the pins in the holes if you have some.
And you're done!
Now you can had the mattress and sheets and all. Be gentle, don't put too much pressure on the frame when you tuck the sheets and duvet.