HP Deskjet 5145 Color Inkjet Printer - Manual (Page 100)

4. Slide the paper guides firmly against the envelopes.
5. Lower the Out tray.
printing
1. Open the Printer Properties dialog box, then select the following:
tab setting
Paper/
Quality Size is: Appropriate envelope size
Type is:
Plain Paper
2. Select any other desired print settings , then click OK .