I like do to this in a notebook. Every time I study a new topic, like, a conjugation or a list of words, I try make a phase with that and something that I studied before. The sentences will become more and more complex as you study new things. My first one was probably "こんにちは"(hello) and this days i wrote "朝にコーヒーを飲みます"(I drink coffe in the morning), so you need do it a lil often and don't be afraid to use things you don't sure how works. Aslo, I like to use this in flashcards (I use anki) when I hide something for try remember that. Like, this last one, the new word was 朝(morning). So my flashcards is: (in the morning)にコーヒーを飲みます and its answer is 朝(あさ)[always include furigana!). And if you don't know how put one word in the sentece, you should search for some senteces examples and copy them estruture. You can do it here, on renshuu's vocabulary lists, or in a translator/dictionary. I like the app "study kanji" for this part, it has a complete dictionary for free.
you can see en example of any type of sentence. Then you can swap out the words to say what you want to say. If you don't know the word, you can look it up in the dictionary.
