You will first want to download and install the Hiro Wallet which can be installed on Google Chrome, Brave, or Firefox browser.
This tutorial will show you how to do it through the Brave Browser.
Google Chrome and Brave link:
Once installed, you should automatically be brought to a similar page.
Click "I'm new to Stacks" button
Save your Secret key and put it in a place where you won't lose it. There should be a hard copy and a digital copy because if you do lose your secret key, you lose your account.
Click the "I've saved it" button
Enter a strong and unique password and then click "Done"
From here, you can choose either option. For me, I usually click "No thanks"
You're all done.
(Optional) Don't forget to pin the Hiro Wallet to your browser. It makes it easier to access.
Click the Puzzle piece icon, then click the Pin next to the Hiro Wallet
At this time, there is no mobile Hiro wallet though one is being developed. There is no expected timeline of arrival.