trimmomatic: command not found

Hello I want to use trimmomatic on Ubuntu. Even though I run the

$ ls trimmomatic-0.39MANIFEST.MF  build.xml  lib  versionHistory.txtadapters     distSrc    src

And get results, when I run this code:

trimmomatic PE SRS3773138_1.fastq SRS3773138_2.fastq \  SRS3773138_1.trim.fastq.gz SRS3773138_1un.trim.fastq.gz \ SRS3773138_2.trim.fastq.gz SRS3773138_2un.trim.fastq.gz \ SLIDINGWINDOW:4:20 MINLEN:25 ILLUMINACLIP:NexteraPE-PE.fa:2:40:15

It gives

-bash: trimmomatic: command not found

Could you help me?