If you are breastfeeding, you could start by looking at these NHS Start4Life articles, with information ranging from how to breastfeed to breastfeeding challenges.
The La Leche League offer lots of information on breastfeeding.
Unicef has lots of useful breastfeeding resources. They also offer lots of helpful bottle feeding resources. If you are wondering if your baby is getting enough milk, have a look at the checklist how to tell if breastfeeding is going well from Unicef. It tells you what the signs are when breastfeeding is going well and when it's best to ask your midwife or health visitor for help.
If your baby is bottle-fed the NHS Start4Life article gives bottle feeding advice.
First Steps Nutrition offer helpful information on infant formulas.
The NCT (National Childbirth Trust) has lots of clear and reassuring information on feeding including useful articles on
The NHS has information on your baby's first solid foods, including when to start introducing solid foods, signs your baby is ready and what to introduce, when and how.
NHS Start4Life also has a section on introducing solid foods, with expert NHS advice, helpful videos, tips from other parents and lots of simple recipes and ideas.
Barnardo's Family Space has a helpful article on breastfeeding and another on solid foods and healthy eating