I'm assuming that your TV has only HDMI ports plus a coaxial cable/antenna jack, and your DVD player and VCR don't have HDMI outputs. You might be able to connect the VCR to the coaxial cable jack, unless you're already using it for cable TV or an over-the-air antenna.
You can purchase converter boxes that convert composite (red and white audio, yellow video) to HDMI, or component (red, blue, green video, red and white audio) to HDMI. Just make sure the box has component or composite inputs, and HDMI output. Some converters do the opposite. Make sure that the input type on the converter box matches the outputs on your DVD player and VCR.