Run Steam -> Community -> Community market.
In order to use the Steam community market, you must meet the following conditions.
[Trading and market use restrictions]
1) If you cancel an accepted trade during delay time, you will be restricted for seven days.
2) Steam abusers cannot use the market.
3) If you login from a new PC or after deleting all cookies from your web browser without using Steam mobile authenticator, you will be restricted from for trading and the market for seven days from the moment of authentication.
4) If it had been seven days or more since using steam mobile authentication, you can still used the market and trading from a new PC or logging in after deleting all cookies.
5) If you have not setup the Steam mobile authenticator, trading and the market will be restricted. 15 days has to pass before using the market after setting up the Steam mobile authenticator.
6) If the account's email authentication is removed or added again, 15 days must pass before using the market.
7) For accounts that have had their passwords reset cannot use the market for seven days.
Changing the password does not restrict the use of market.
8) For accounts that have not logged in for the past two months, the market use will be restricted for 30 days.
9) Adding a steam mobile authenticator and trading items within seven days, can cause a delay maximum of 15 days.
10) If you remove the Steam mobile authenticator, market use is restricted for 15 days.
11) If you add a new payment method, you can use the market after five days.
If you verify another credit card, you can access and trade in the market before 5 days.
12) Your account must have a valid purchase history within 30 days - 1 year in order to access the Steam community market. Registering a CD key or gifts are not included.
13) For accounts that have been blocked by the VAC cannot trade PUBG items.
14) If you change your email address attached to the account, you will be restricted from trading for five days.