How to adjust cable length on integrated brake/shift levers, when there is no barrel adjuster?
If there's no barrel adjuster, then you'll need one installed. Ask LBS to do that or do it yourself:


Get an inline barrel adjuster and two 4mm ferrules. These are pretty cheap.
Get tools to cut cable housing.
Make sure there is enough shifting cable left to accomodate extra 3-4 centimeters added by adjuster. If it's too short, get a new cable.
Detach cable from derailleur.
Find a straight section on cable housing that doesn't rub anything and mark it.
If your frame runs cable bare and not through inner liner, attach a long string to cable end before pulling it out. This will help to route cable back.
Cut housing in marked location, install ferrules on both ends. If ferrules have long tongues, cut them down too.
Adjust the adjuster to shortest position, install it in the cut.
Route cable back using the string. Now you can tweak cable tension for front derailleur.


The result should look something like that. As a side note, 5800/6800 derailleurs have more complicated installation procedure than older models, make sure to download dealer's manual and read carefuly for instructions.