To use a pricelist in Odoo, you can follow these steps:

1. Go to the Sales module in Odoo and click on the "Configuration" menu option.
2. In the Configuration menu, select "Pricelists."
3. Click on the "Create" button to create a new pricelist.
4. Give your pricelist a name and select the currency that you want to use for pricing.
5. Under "Pricelist Type," choose whether you want to set the pricelist based on "Products," "Product Categories," or "Variants."
6. Under "Apply On," select the field you want to base the pricelist on, such as "Sale Price," "Cost," or "Public Price."
7. Set the pricing rules for the pricelist. For example, you can set a percentage increase or decrease from the base price, or you can set specific prices for individual products or categories.
8. Save your changes.

Once you have set up your pricelist, you can assign it to customers or customer groups in the Sales module. To assign a pricelist to a customer or customer group, follow these steps:

1. Go to the Sales module and click on the "Customers" menu option.
2. Select the customer or customer group you want to assign the pricelist to.
3. Under the "Sales & Purchases" tab, select the pricelist you want to assign to the customer or customer group from the "Pricelist" drop-down menu.
4. Save your changes.

Now, when you create a sales order or a quotation for the customer or customer group, the pricelist you assigned will be used to determine the pricing.