Welcome to the forum @Mizztraveller !
You can find some info here in this blogpost
and here
Important to new sitters is to get reviews from sits, as this is important to get sits. Not as impossible as it seems. See if you can get some short local sits to start. A night, a weekend etc. For local sits you might be avle to offer to meet the petparent before the sit, which can help you when you don’t have reviews, and it is an advantage also to the host as can meet the pets and show the routine pre-sit. Getting some experience will also teach you what you need to look for and ask for so that you get sits that match your preferences and criteria. This is a mutual agreement, after all.
Forum is a great place to learn and ask for help, so - welcome!