The -たら form of verbs, adjectives and nouns describes condition that once fulfilled, the rest of the sentence happens.
Verbs
時間がったら行きます。
If I have the time, I’ll go.
i-adjectives
お天気が良かったら、公園に行きましょう。
If the weather’s good, let’s go to the park.
na-adjectives
暇だったら、遊びに来てください。
If you’re free, please come round.
Nouns
いい天気だったら、歩いてきます。
If the weather’s good, I’ll come on foot.
Note that with this construction, the -たら phrase is a condition that has to be fulfilled before the rest of the sentence can happen. However, unlike -と, it is not the cause of the second half of the sentence, and there is no sense of inevitability. Something else could also happen.