Using an English or Spanish dictionary
Moving to a target language dictionary is a valuable step in learning a language when you've acquired enough vocabulary to be able to understand most of the definition. Thus, it's probably too tedious at the beginner stage but beginning in the intermediate level, it can be really helpful.
Often a word in one's target language can be translated in several ways so context is key.
A good dictionary will provide several numbered definitions, along with an illustrative sentence.
In this way, you get to see how the word is used in specific contexts and whether there are commonalities among the usages that may not pertain in English. That is, in only one of the definitions does the word translate into one English word while other definitions may require different English words. And vice versa!
You probably won't need the more elaborate definitions all of the time but reading a definition in Spanish provides yet more exposure to the language and you undoubtedly will pick up additional vocabulary and reinforce grammar patterns. This doesn't mean you have to run off and buy a Spanish dictionary in Spanish. You can start by reading the definitions of the word in Spanish on Google. If you understand them, great, if you have to look up one new word, not problem but if most of the definition doesn't make sense, there's always the English as back up. Be careful, as I'm sure you've already encountered, what seems like an English cognate does not necessarily mean exactly the same in the Spanish so checking in the dictionary is always a good idea.
You can use both. If you don't understand the explanation in Spanish then you can check the translation in English. But sometimes even if you understand the explanation in Spanish you might not know what the word exactly represents. Unless you use a very simple dictionnary, the definitions can sometimes be more complexe than the word itself. Personnaly I started using a Spanish dictionnary when I was translating texts at University, because I needed a very precise definition of the words to translate them properly in my language, and then when I was living and studiyng in Spain. But before that, if I couldn't guess the meaning of a word from the context I just cheked the translation, just like you do on Lingq. It's faster.