Depends on the phrase, but even if it's not in the dictionary you can make a custom term for it. Do you mean phrases like よろしくお願いします(よろしくおねがいします)? There are also full sentences you can study.
Edit: Sentences and phrases are not the same thing, but if you were asking for sentences/grammar you can add those schedules from "Manage your schedules to change what you are studying, freeze schedules, and more!" (bottom of your schedules on the Dashboard) → "All schedules":
You can also make your own schedule from "Make my own" (two over to the right of "Renshuu recommended").
Alternatively, you can schedule any Sentences lists you'd like from "Community Lists". You can also make your own list(s) from the ME tab → "New List".
Yeah, some people learn mainly like that when they start. Like polyglot or those who focus on speaking (usually in language exchange community by asking directly to natives).
Focusing on words allow you learn words in bulk, be able to recognize them but not really to use them. Focusing on sentences allow to quickly learn practical things, which very satisfying when you're able to use them with natives, but it's also feel "slow". Because you usually learn some precise context/usage/nuances (which is why you're become able to use those words correctly) and that takes more energy than just learning words individually.
Anyway, on renshuu, you can either use a pre-made sentences list, search for sentences under each words or by using the look-up features in the dictionary.
Click on Manage your schedules after your schedules in the dashboard, then All my schedules -> Make my own -> Sentences and after that you will be able to either add pre-made lists, individual sentences or your own sentences that you found elswhere.
My responce will sound insane but there are words in phrases. (Not trying to be rude) but 'A を ください。'is 3 whole words if you count particles with A being what you want, を being a action particle and ください meaning please. Language is crazy. Even in English 'Can I have "A" please' has 5 whole. Words in it. So technically when you learn a phrase, you are learning words at the same time. As I said before, it is crazy in all languages.
. As I said before, it is crazy in all languages.