I've just started brewing my own beer, followed the instructions meticulously but my SG reading was 1035?! I thought this had to be around the 1045 mark? Was I still good to add the yeast and start the fermentation process?
Making the assumption that it is and extract kit using top up water it is likely that you didn't get a good mix and sampled an area with more water. If you used all the ingredients and ended up with the right amount of wort in the fermenter your SG will be within a point or two of 1.045.
You should be good to go. Wait at least 10 days before you mess with it any more. I do primary only (no secondary) and leave it be for 3 weeks before doing anything.
Agreed. when using top up water you should give it a good mixing. If for nothing else to introduce enough air to get it to ferment. 3 weeks is a really good marker for the yeast to ferment then clean themselves up. Happy brewing.