Hi Sharon, 

Freezer jam always has a softer set than cooked and canned jams. If you are looking for a very firm set, the best approach is to cook the jam and add pectin. Depending on whether you're using liquid or powdered pectin, the instructions are slightly different, but you can find full instructions on our website at this link.

If you want to minimize cooking and stick with a freezer jam, you can also follow these instructions: 

In a bowl, mix jelly or jam and 2 Tablespoons sugar for each cup of jelly or jam. Stir well until dissolved (about 3 minutes). 

Measure 1 Tablespoon water and 1½ teaspoons powdered pectin for each cup of jelly or jam. Place in small saucepan and place over low heat, stirring until the powdered pectin is dissolved. Add to the sugar and fruit mixture and stir until thoroughly blended (about 2-3 minutes).

Pour into clean containers. Cover with tight lids. Let stand in refrigerator until set. Then store in the refrigerator or freezer.

Thanks for using Ask Extension!

Jared