Before you queue
Open the official experience and choose Casual for the first sessions. Casual is first to 8 round wins. The Roblox listing caps a server at 14 players. Unranked Competitive is a separate 5v5 mode and is a poor place to learn the buy menu.
You are placed on Terrorists (T) or Counter-Terrorists (CT). If the game says a team is uneven, join the smaller side. Press M when you need the team menu later. Switching teams in the middle of a match can wipe the round counter used for end-of-match Credits.
What wins the round
Terrorists try to plant the C4 on a bomb site and keep it from being defused. Counter-Terrorists try to stop the plant or defuse a planted bomb. Eliminating the entire enemy team also wins the round.
The bomb timer is documented at 40 seconds after a successful plant. Round clocks are not consistent across public writeups: mode tables list 2:00 for Casual and Unranked, while a game overview also says 1:45. Use the timer on your HUD for the server you are in.
Freeze time and the buy menu
At the start of the round you are in spawn with round cash, not Credits. Press B to open the buy menu. Terrorists start on a Glock-18 (also listed as Glock-17). Counter-Terrorists start on a USP-S or PX4. Those pistols can be bought again for $200 if you drop them.
On a pistol round, a common upgrade is the P250 at $300 or a Desert Eagle at $700 if you saved cash. Do not spend Credits here. Credits only open cosmetic cases.
During freeze time, inside the buy zone, right-click a purchase in your inventory to refund it. After you leave spawn, the menu closes.
Plant and defuse
Terrorists equip the bomb with 5, stand in the marked site, and hold left click or E to plant. Counter-Terrorists walk up to a planted bomb and hold E to defuse. Documented defuse time is 10 seconds, or 5 seconds with a Defuse Kit ($400, CT only). One controls summary quotes only the 5-second figure and skips the kit split, so check whether you actually bought the kit.
After the round
Round cash carries into the next round of the same half and is spent on guns, armor, and grenades. Credits, if you earned any, appear for the cosmetic shop and are not the number in the buy menu. When you are comfortable with one bombsite, move to the map notes and the weapon list.