The easiest way is to run
fg to bring it to the foreground:
$ help fg
fg: fg [job_spec]
Move job to the foreground.
Place the job identified by JOB_SPEC in the foreground, making it the
current job. If JOB_SPEC is not present, the shell's notion of the
current job is used.
Status of command placed in foreground, or failure if an error occurs.
Alternatively, you can run
bg to have it continue in the background:
$ help bg
bg: bg [job_spec ...]
Move jobs to the background.
Place the jobs identified by each JOB_SPEC in the background, as if they
had been started with `&'. If JOB_SPEC is not present, the shell's notion
of the current job is used.
Returns success unless job control is not enabled or an error occurs.
If you have just hit Ctrl Z, then to bring the job back just run
fg with no arguments.