Talk to her about everything. Anything she signs, points to, uses, you assign the word. Give her a moment to repeat after you (she will eventually,) and confirm the word. The next step is then adding on. "Truck, yes blue Truck!"
Just make sure to keep verbalizing everything. If you're signing to her, make sure to say the word as well. Each baby will go at their own pace, but eventually she will catch on to which words are associated with which signs.