OK if the dts client is installed then you just need to load the package and run it.
The /F parameter on dtsrun will load the file and run it.
You can also use sp_oacreate which will allow you to change properties of the package before running it.
This will enable you to do anything you did with enterprise manager but not as easily. Save the package afterwards or you can use it to run the package and make any changes on every run.
Probably better to use it to set global variables and use them within the package.
see
www.nigelrivett.com
sp_oacreate Load DTS