How do you fit a micro sd card into a samsung gt-s5230?

Relatively simple. Take the battery cover (the back of the phone) off. Remove the battery.

Place the simcard in, gold pins down. Examine the battery 'hole' you will notice a further hole that goes underneath the sim card.

Take your micro-sd card, gold pins facing towards the sim card and insert carefully. Press until you feel a spongey texture, press in all the way, then release.

Remember: under the sim card, means that you need to remove the battery.