This can be fine from the off, particularly if you have bought locally and had the bike set up for you at the shop. However it is increasingly common to buy online, so it may take a little experimentation over time to get right, but it is worth getting really comfy on the bike, then you are not distracted or discouraged by any feelings of discomfort, and in fact are then pedalling most efficiently!
First make sure the saddle is initially set to the midpoint on its rails where they sit in the seatpost clamp, leaving a centimetre or two clear rail either side of the clamp point, and the saddle top looks level on the seatpost.
Now set the correct saddle height for comfort and effective pedalling. To do this use a wall or another person to stabilise the bike so you can sit properly on it and put one foot on a pedal, with that pedal down at its lowest point.
Now set the saddle height such that this leg is just slightly bent at the knee. (This can feel too high initially, especially if you can’t put your feet flat on the ground, but it is correct, makes for more efficient cycling and will be much better for your knees, and if necessary you will get used to propping yourself up with the an extended foot or even popping off the saddle to stand when you are stopped at a junction or whatever.)
Now, set your preferred handlebar height.
Hybrid bikes often have height and reach adjustable stems fitted as standard to make it easy to alter these parameters as you prefer, but if not you (or a bike shop) can use spacers, different angle stems or even stem raisers to sort this.
On a Hybrid bike start by setting the handlebar grips, where you hold on, visually at the same height as the saddle, or a little higher.
The resulting uprightish stance will be great for your joints, and for seeing and being seen. (On ‘Dutch’ style bikes, usually of the ‘step through’ or ‘easy entry’ frame style they will already be higher than the saddle.)
Now check the reach. Getting this parameter right – how far you are reaching forward when you are sitting on the saddle and holding the handlebars to ride – will help avoid backache on longer rides.
If it only feels a tad out, then moving the saddle backward or forward a smidge on its rails will sort it. If it needs more than this, then swapping to a longer or shorter stem will do the trick. This particular parameter may be more of a trial and error process over a few rides.
(NB A good way to get a sense of reach being correct is to note if you periodically find yourself shuffling your bum back (reach is too short, you are too near the ‘bars), or forward (too far away.)
Finally consider if the saddle angle is right for you. You want to ensure you don’t feel your weight is ‘thrown forward’ onto your hands, but is evenly distributed between those parts of you that are on the saddle and the handlebars. For some people, setting the nose a little higher is better than having it level.