Here is a recipe that will show you how to make pickle relish for canning:

6 lbs. Cucumbers
2 ½ cups white vinegar
2 lbs. Onions
5 cups white sugar
3 green peppers
2 tbsp. Mustard seed
2 red peppers
1 tbsp. Turmeric
½ cup coarse salt
10 cups boiling water
2 tbsp. Water
2 tbsp. Cornstarch

Process all vegetables through a food chopper and put into a very large cooking pot. Sprinkle with salt and pour boiling water over all. Cover and let stand overnight. Drain well. Add vinegar, sugar, mustard seed, and turmeric. Bring to boil over medium heat stirring often. Boil slowly for 30 minutes. Stir cornstarch into cold water and stir into boiling pickles until slightly thickened. Pour into sterilized Jars.

Some call this the Million Dollar Relish. So now you know how to make a pickle relish.