Hi Sd Micro If there is a reference sequence for your plasmid you can use the prokka (https://github.com/tseemann/prokka) tool to annotate and specify your reference sequence as proteins to annotate from. I made a tutorial on genome annotation that you can find here ( https://youtu.be/MqDhhuIXjgg ). The parameters I specified will also work for plasmid.
Aside Prokka you can also use PGAP to do the annotation(https://github.com/ncbi/pgap).
You can also compare your sequence to other plasmids using BRIG software. This tutorial shows you how to do it ( https://youtu.be/pobQgE4z-5Q )