There are actually more than six steps, but the main ones are as follows:
1. By the first Monday in February the President submits budget to Congress.
2. February-September Congressional phase. Agencies interact with Congress, justifying and explaining President’s budget. The House and Senate Committees on the budget draft budget resolutions. The budget resolution is a kind of blueprint for actually appropriating money for the budget. Differences between the House and Senate budget reports are resolved in a conference report which then needs to be approved by both houses. The budget resolution is supposed to be pased by April 15, but this date is often missed.
3. Discretionary spending (as opposed to entitlements like social security) is in the form of appropriation bills, involves annual actions that must be completed before the beginning of a new fiscal year. These bills much be passed by both houses of Congress.
4. Within 10 days after approval of a spending bill (in some years such bills may not be passed, see below), Federal Agencies submit apportionment requests to OMB for each budget account.
5. Within 30 days after approval of a spending bill, OMB apportions available funds to agencies by time period, program, project, or activity.
6. October 1 Fiscal year begins.
In practice, the budget process often gets delayed and the Congress has to pass continuing resolutions in order to keep the government operating.