A couple of questions

Question

I have a couple of questions:How to determine when to use en/el or no article in
sentences like Me gusta ir a la playa en verano From the exercise:I like going to the
beach in summerKwizbot     Me gusta ir a la playa en verano 
You            Me gusta ir a la playa
el veranoIn writing the adjective for this next section, it made me realize that I need info on forming adjectives and wondered if you have  any lessons on forming adjectives:For example, from the test:Re: is
very relaxing

Kwizbot     es
muy relajante 
You            es muy relajadoThank you,Nicole

Answer

Hola Nicole
I am not quite sure about your first question. Do you refer to preposition "en" for "in summer"? 
In summer, in winter, in spring, in autumn... we use preposition "en" for all these, the same as in English.
If you refer to using both the preposition en + el, then I can tell you that you could also say it like this:
Me gusta ir a la playa en el verano. 
However it is less common to say this this way. We'd probably use it with "el" if we are more specific about a specific summer, for example:

Conocí a Roberto en el verano de 2010.
I met Roberto in the summer of 2010.

As per your second question about forming adjectives, there are different endings for adjectives. They could be regular adjectives ending in -o/-a (rápido, rápida, oscuro, oscura, feo, fea...), or ending in a consonant (difícil, circular, especial, feliz...) or ending in -e (triste, inteligente, importante...) It is a question of learning vocabulary.
Saludos
Inma