You don’t have to change your guitar strings at this exact moment, however it will be an important skill to have as you advance as a guitar player. Indications that your strings need to be changed are if they look or feel rusty or discolored. Another sign your strings have reached the end of their life is if they simply won’t stay in tune, even after tuning them. There are a few factors that affect string longevity. The first circumstance that you may not be able to do much about is the climate you live in. Guitars will ideally be stored in a humidified environment to protect the wood, which can be difficult to maintain if you don’t have the resources.
The next best thing you can do is purchase a case humidifier and store your guitar in a hardshell case when you’re not playing it. I recommend the Humitar made by MusicNomad. A more avoidable detractor of string life is dirty hands and finger tips. Your fingers produce oils that can wear down strings, so it’s important to remember to wash your hands before you play your guitar, and wipe it down with a cloth when you’re done. The last thing that affects string life, which isn’t necessarily a bad thing, is how often you play your guitar.
Obviously, the more you play, the more you improve, so you don’t want to stop playing just to prolong string life, as packs of strings are only $10-15 dollars and will last the average player at least 3-6 weeks. As long as you pay attention to the climate and cleaning your hands, you should enjoy a nice amount of string life for every pack you purchase.
Most electric guitars come with .10 gauge strings, and you can purchase a variety of brands at your local music shop or online. The lower the gauge, the lighter the string. Starting out, I recommend Elixir Optiwebs .10 gauge strings.