From SpanishDict

enchufe
2. (colloquial) (influence)
a. connections
Yo estoy mejor cualificado, pero le dieron el trabajo a ella porque tiene enchufe. — I am more qualified, but she got the job because she has connections.
b. friends in high places (colloquial)
Tengo un enchufe que te puede ayudar a conseguir un aumento. — I have some friends in high places who might help you get you a raise.

Someone who is enchufado would be "well-connected" or "a well-connected person".

Less formally, you could say "know someone" or "hook up"

• He got the job because he knew a guy/someone (at the office, on the board, etc.)
• My friend hooked me up with the job.

From SpanishDict

enchufe
masculine noun

2. (colloquial) (influence)
   a. connections
   Yo estoy mejor cualificado, pero le dieron el trabajo a ella porque tiene enchufe. — I am more qualified, but she got the job because she has connections.
   b. friends in high places (colloquial)
   Tengo un enchufe que te puede ayudar a conseguir un aumento. — I have some friends in high places who might help you get you a raise.

enchufado
adjective

1. (colloquial) (favored)
   a. well-connected
   Mariano consiguió el puesto de gerente solo porque está enchufado.—Mariano only got the manager position because he's well-connected.
   b. no direct translation
   ¿Sabías que Jaime está enchufado en la empresa de su tío?—Did you know Jaime's got a job in his uncle's company just through his connections?
   Esto está lleno de gente enchufada.—This place is full of people who got a job because of their connections.

masculine or feminine noun

2. (colloquial) (person with connections)
   a. well-connected person
   En esta empresa solamente los enchufados consiguen un aumento de sueldo.—Only the well-connected people get a raise in this company.
   b. person with pull
   Le di mi nuevo disco a un enchufado que trabaja en la discográfica.—I gave my new album to a person with pull who works at the record company.

As is often the case, there does not seem to exist a direct translation. Although connected and well-connected might not necessarily have negative connotations, they can still be perceived negatively under the right context.
Example.

• He's obviously underqualified. I bet he got the job because he's got connections.

Less formally, you could say "know someone" or "hook up":

• He got the job because he knew a guy/someone at the office (on the board, etc).
• I didn't need to apply. My friend hooked me up with the job.