There are a couple of options.
1. Bring up the list of DTS packages. Right click on the DTS Package and select Schedule Package. Select the schedule and click OK or Save.
2. Create a new job, and add a job step. The step type will be Operating System Command. The command to run is dtsrun.exe. You can run this from a command prompt with /? to see the list of options.
If you use the first technique it simply creates a SQL Job for you, so the end result is the same either way.