In order to apply customer specific pricing you will need to ensure you have added the customer or the customer has placed an order with you in Supply'd already.

To apply customer specific pricing go to Customers then click on a customer and go to the Pricing tab and click Add.

Fill out the fields based on the guidance below:

Categories Defines the categories that the discount will apply to. You can select as many categories as you would like. 
Products Defines the products that the discount will apply to. You can select as many products as you would like. 
Discount % Defines a percentage discount you would like to provide. For example if you provide a 20% discount to the customer on the categories or products defined in the Categories and Products fields that you would add the value "20". Leave blank to not apply a discount percentage.
Discount $ Defines a dollar discount you would like to provide. For example if you provide a $5 discount to the customer on the categories or products defined in the Categories and Products fields that you would enter the value "$5.00". Leave as "$0.00" to not apply a discount dollars.
Price Override (Set Price) Defines a new price for all the products and/or categories selected in the Categories and Products fields. For example if you would like to set a new price of "$5.00" you would enter the value "$5.00". Leave as "$0.00" to not apply a discount dollars.

Click Save to apply the new discounts to the customer.

To edit a discount click on the discount under Customers > (Select Customer) > Pricing click edit on the pricing you wish to change. 

To delete a discount follow the instructions to edit above then scroll down to the bottom. Click Remove Discount then confirm deletion to remove the discount.