The steps for sellers to set monthly sales goals on Taobao are as follows:

1. Log in to your Taobao seller account, and on the Seller Center page, click the "Data Center" option.

2. After entering the data center, select the "Store Overview" option to enter the store overview page.

3. On the store overview page, you can see some basic data information about your store. Select the "Marketing Promotion" option.

4. Click the "Monthly Plan" option in the "Promotion Management" menu to enter the page for setting the monthly plan.

5. On the monthly plan page, you can set sales targets and activity plans for this month. First, you need to click "Make Sales Plan".

6. In the pop-up window, enter the specific target value and time range.

7. After the goal is set, a chart will be displayed at the bottom of the page to view the completion status. In addition, you can add or modify other marketing activities by clicking the "Promotion Plan" button.

8. After completing the setting of all goals and activity plans, remember to save and start the plan in time.

Sellers should set reasonable and feasible sales goals for themselves and formulate scientific and effective marketing strategies to achieve this goal. At the same time, they should constantly track and monitor sales data, and make adjustments and optimizations to achieve better results.