That bolt only adjusts the height, the bolt (s) you need are the ones just below the saddle that adjust 'tilt' and 'fore and aft' movement.Loosen off the pinch bolt on the frame at the bottom of the seat post, usually a Allen key, and realign it by eye.
Depends which way it's not straight. Being spun is more common than getting tilted IMOThat bolt only adjusts the height, the bolt (s) you need are the ones just below the saddle that adjust 'tilt' and 'fore and aft' movement.
Left/right"Slight angle" ....up / down or left / right ?
Yeah could be but it was the way the OP said 'tilted' as opposed to twisted.Depends which way it's not straight. Being spun is more common than getting tilted IMO
Aah it is the bottom (clamp) bolt that needs to be undone then retightened after adjustments then.The saddle needs adjusted left / right
Why not consider investing in a simple bike maintenance book @Glasgow44 . Please don't take this as me having a go at you, but if you don't know how to straighten a saddle in the horizontal plane, then there will be lots of really interesting information in the book to help you with other basic stuff.
With regard to your seat post, it'd be worth pulling it out completely, cleaning it off, cleaning the inside of the seat tube off, smearing a bit of grease on and then replacing straight and as @vickster says, at the right height (sit square on the saddle and have the saddle at a height which has the heel of your straight leg on the pedal at 6 o'clock (starting point)).
The Haynes bike book is a good way to learn about bike mechanics. Plenty of photos to help you as well as a step by step guide .No offence taken at all mate. You're absolutely right. I just got a bit confused as there are too many/so many bolts, etc and I didn't want to mess it up!