Some online resources for translating Spanish phrases are Wordreference.com, Linguee's online translation dictionary, Oxforddictionaries.com and Dictionary.reverso.net. The resource best suited to you depends on your level of knowledge.
For a novice learner of Spanish, Wordreference.com, Oxforddictionaries.com or Dictionary.reverso.net are good choices. These online dictionaries allow you to search for individual words and provide several example phrases of how the word is used in phrases in everyday conversation.
Linguee.com is excellent for those who have a solid understanding of Spanish already. You can search for any single word or phrase and the site will quickly return several translations of that word or phrase in real contexts that have been translated online throughout the world.