If you're not sure where to start with strength training, check out the fitness section. Coach Nicole has a bunch of short 10-15 minute ST routines you can try at home. www.sparkpeople.com/resource/videos-detail
At some point, you're going to need heavier weights because what the videos don't tell you is that some muscles are stronger than others. 5 pounds might be challenging for a shoulder press, but it won't be enough for a chest press or rows. Don't be afraid to use weights between 8-15 pounds. Women are stronger than they realize. Also, you will NOT get bulky if you start using a 10+ pound weight. that's a misconception. Women don't pack on muscle the same way men do. But, we do both benefit from regular strength training.
Buying hand weights can be expensive. You might consider buying a set of resistance bands. resistance bands are a great way to strength train if you don't have access to heavier weights.
You might want to also find these books at your local library. they are excellent beginner strength training books that will teach you the basics.
Bill Phllips "Body for Life"
Cosgrove "New Rules of Lifting for Women".