I still have swelling in my knee after a arthroscopic knee surgery for a torn meniscus from a year and a half ago. How do I get rid of it? Is it bad?

Knee swelling. It is possible you have some persistent irregularity or some arthritis, further tearing, or synovitis /inflammation. Check with doc if still locking for you.
See your surgeon. The swelling may be due to arthritis which is poorly treated with an arthroscopy. It is usually not an indicator of immediate danger but is bothersome. Sometimes an injection can help reduce it.