For the first time to inject gear make sure you've researched plenty, got your course spot on and even better if you've got an experianced friend there for the first time, start off with injecting no more than 1ml, best place to start with is upper right of the arse cheak or in the quad, the first time i injected was into the delt, it may hurt it may not everyone is different and its also down to the gear and who makes it but you should get used to it!
and always leave a liitle bit of the pin out incase it snaps and you'll be able to get tweezers on it to pull it out!!!