1) Be aware of what it the min/max limit of your device in order to purchase the correct SD card. This can be accomplish by reading your owners manual or searching the web for the devices specs page.
2) once you've located the correct min/max limited SD card, you would turn off your device, removed the cover/s locate the SD card slot. As seen in this image.
View attachment 239387
Do not get confused when seeing multiple slots, Some devices actually allow for 1 or 2 slots for a MicroSD card or external memory.
3) Once the SD card has been placing into the slot, replace the rear cover, and turn the device back on. Typically the device will display a message indicating that the SD card has been recognized. One you see this message and the dives is at full power or operation, locate the settings menu, access the storage option/setting then click the microSD card and look for "erase SD Card" command
IMPORTANT: It's best to format the card while it's attached to your smart phone and not the computer. In this case when the card is being formated, the phone assigns a number of hidden files towards the card which the phone need in order to use the card. If you format the card via the computer, the Computer would assign hidden files that may not be comparable with your phone operating system, thus one could see error message of the card could become corrupted or even unusable.