First, position is key. Have a firm grip on the pistol with your strong hand (the one you write with). This should be similar to your shooting grip. You can pull the gun in closer to your body. With the weak hand, cup the top rear of the slide, it is often ridged for an easier grasp, being careful to ensure that your hand does not extend over the ejection port, and pull straight back while pushing forward with your strong hand. Pull the slide straight to the rear, and then let it go. Yes, let it fly, if you hold the slide as it is returning to position you can create several issues such as a mis-feed, failure of the gun to return to battery (ready to fire). This takes practice. It is also harder on tiny gun, you may need to adjust the position, but…you can do it!
If you need to strengthen your hands, there are products available for that purpose. My personal favorite is the GripMaster , available in multiple resistance levels at Amazon.com. It can be used to work the fingers individually. The other advantage to this exercise is that is helps with your trigger control. Some triggers are harder to pull than others. Ironically, the triggers on revolvers, which do not have a slide and are often recommended to women, have a harder pull than many semi-automatics.
Lastly, a good instructor can help you to adjust your hand positions so that you can be effective. Don’t hesitate to ask for help. If you are at a range that has NRA Certified Range Safety Officers, they are all instructors, and therefore can offer you some advice or assistance if you need.