As a new runner, it’s better for you to start with trying to increase the distance (or time, if you prefer to measure by time) of your runs. As you build up your endurance, your speed will also improve.
Don’t rush into formal speed training, such as interval workouts, just yet. Doing too much running at too high an intensity is an easy way to get injured. After you’ve been running for about two months and have a nice base, you can start by adding strides into one of your weekly runs. You can also try picking up the pace towards the end of one of your runs. Wait until you’ve been running for 3-4 months before you start to add tempo runs, fartlek runs, or interval workouts.