Take your measurements! Most brands post sizing charts for their clothing online, and you can use those as a good reference with what should fit you best.

Totally get you on shopping in person being intimidating. Shopping online can be great when they have charts, but make sure to read the reviews too!! See if people say that the clothing in question runs small or large, or if it's generally true to size. That can give you an idea of if you should size up or down from what the chart says.

In cases where there's no chart, you gotta give it your best guess. Sometimes, brands will list some of the basic measurements in the item description box. But ultimately, you're gonna wanna know what the return policy is and how you can go about returning items that don't fit quite right.

Sadly, there are some things that can be very difficult to size online, like bras, for instance. Going with bralettes or bandeaus or sports bras will be much easier at first. The subreddit a bra that fits has a calculator online that can help you out with finding your bra size using your measurements when you're ready for that.

Personal advice, but if you're new to women's fashion and interested in styling for your body there are so many guides online to dressing ways that will flatter your figure and look great on you. They're not the be all end all and you shouldn't feel confined 100% by what they say, but if you're like "I don't even know what would suit me" it can be a great way to get some ideas :)