First, cut open the grout packet with your scissors and measure it out. Pour the grout into your empty bucket. Pour in the water and stir it into the grout. Make sure you stir right around the bucket and add more grout or water if necessary. Keep stirring until the mixture has a ‘smooth toothpaste' consistency without any lumps.
Once you have the grout consistency you want, leave the mixture to stand and thicken up. After about five minutes, give the mixture another stir. To test if it is thick and firm enough, hold up your stirrer. If the grout mixture just hangs and doesn't drip, it's ready to use.