How Do I Make Up Formula Milk Bottles?

Follow the instructions on the side of the tin EXACTLY.  You will need to sterilise all teats and bottles (although some sources argue you can stop sterilising after 6 months).

You should be very careful about this.  There is always a small risk of micro-organisims contaminating formula feed and bottles.  Moreover, your baby needs the exact ratio of water to powder that is described on the instruction tin.  If a very young baby has too much water that could be hard on their kidneys and may impede their growth.  Too little water and there is a risk of dehydrataion.

Even though formula may seem quite expensive, whatever you do, don't feed non-milk food to a very young baby (under 6 months ideally, but certainly not under 16 weeks).  Their digestive systems aren't ready and the too-early introduction of non-milk foods may cause future health problems.

Bottles should be made up fresh for each use.  If you need to prepare a bottle ahead, the best thing to do is to keep just water very hot in a flask and add it to the powder in the bottle right before use.  The formula will need to cool down before baby can drink it.