Phrases and clauses differ in two respects. A phrase is a group of words that lacks a subject and a predicate, which makes it a dependent construction that cannot stand on its own. A clause is also a group of words, but a clause can be either dependent or independent and usually includes a subject, a predicate or both.
From Phrase to Clause
Determine the phrase you want to change into a clause. A phrase can be a single word or a few words, but should lack a subject and verb. For example, the prepositional phrase "in the house" does not include a subject or verb and cannot stand on its own as a complete sentence.
Include the subject that performs the action of the verb. Generally, subjects of sentences are nouns such as a person, place, animal or thing that is capable of performing an action. For example, a possible subject for the prepositional phrase "in the house" is "Joey."
Include the predicate or verb you want the subject of the sentence to perform to the phrase that you are transforming into a clause. For example, add the past tense of the verb walk (walked) to the phrase "in the house." Now the phrase "in the house" reads "Joey walked in the house" and is an independent clause.
Determine whether the new clause is independent (can stand alone as an independent sentence) or dependent (needs an independent sentence to stand with it to be grammatically correct).
Warning
For academic writing always double check your work against a reputable grammar text for correctness.