A pre lockdown photo of my lovely client working on her press ups.
If you find full press ups hard, start with a more upright surface to place your hands against. I often start my clients doing a press up against the wall, the further the feet are away from the wall the tougher they will be. When this gets easy, find a surface that’s a bit lower like a bench or chair. Continue lowering the incline until you feel confident to try the full version. Aim for core engagement, squeeze the glutes and push your feet and hands into the floor, maintaining a good plank position throughout. Think quality over quantity.
These are much more effective than doing press ups on your knees which do not challenge your core as much. A strong core is key to executing the full version properly.