OP, to answer your question:

Follow the cable from the FR der, under the frame, and up the downtube until the bare cable runs into the housing that leads to your bars. At that juncture, there is a barrel adjuster. Give it a turn to the left and try shifting again.

You may have to do this a few times to get it right.

I suspect this is a new bike and it was fine when you bought it but has developed this problem? If so this is normal with a new set up. You should start having the same problem with the rear der soon, as well. One these are set yo should be good for quite some time.

If you continue to have problems some more detailed info about your particular bike would be helpful.