For chain maille, particularly jewelry made with fine jump rings like these, the jump rings need to be closed under tension. To do this use 2 flat-nose pliers and gripping both sides of the ring push the ends of the ring a little further than closed so the ends overlap, then bring the ends back to meet. There is usually a little clicking sound when they go from overlapped to meet perfectly. Check by feel or use magnification. If your rings aren't right keep adjusting and overlapping till you get a perfect ring.