Currently Flex works with a Surf wallet. Get it for a device of your choice (desktop is also available) and activate your account.
Then get some EVERs on your Surf:
  • you can buy some in Surf directly
  • you can use the bridge to transfer coins from some other network to Everscale, and then send the coins you transferred to Surf
Optionally, you can also accumulate some TIP3 tokens on your Surf account. If they are listed on Flex, you will be able to deposit and trade them.
Once you have some EVERs (overview of the costs of using FLEX can be found here) on your main Surf balance, you are ready to connect your wallet: