I really need new glasses but cannot afford them. How do I get some? Can I put new lenses in old plastic ones?

Replace lenses. Most optical shops can replace the current lenses with new ones, using the old lenses as templates to grind the edges to fit in the old frames. This can cut the cost if the old frames are in decent shape. You can also search thrift shops for a frame you might like and do the same thing. You will, however, need to pay for an examination to determine the power of the new lenses.