You need to send a business letter with your resume.  You can try to run your envelope through your printer.  It depends on what kind of printer you have.  The new printers have a set up for you to insert the envelope, in the printer and click the print button.  On some printers you have to know the size and what setting to use to successfully print your envelope  A business envelope looks better if it is printed, and not hand written.  Personal envelopes are OK hand written.

If you don't have a personal printer, try going to a library and see what they have that is available to use.  I would advise you to try and purchase a cheap printer to use with your computer.  Follow the directions on the  purchase guide for setting up an envelope.

On some computers you can use the letter you are sending  to the print the heading on the envelope.  It depends on how knowledgeable, you are about the printer.

Last but not lease, go to a computer store and ask for directions on how to set up the printer for a letter., and envelope. You need to send the return address, and the to heading, at the same time.

It is not easy to master the sending a professional envelope.  You could try and print the envelope on a typewriter! Get with the modern way of doing business.  You will have to go out and check with other sources, but, you will know how to send the letter next time!