Spray a little silicon or 3in1 oil at the two locations identified by arrows, below. After you lubricate the two areas, unlock the lateral and move the table top back and forth several times to work the lubricant in. You may have to repeat this.
Note that you are applying lubricant to what look like brass washers. These bushings are made by adding oil to the metal as the material is compressed. Friction during use causes the oil to seep and movement will become easier with use.