2 Answers

You'll have to check these websites for your owner's manual. Many require your e-mail address to send a download link to (I can not guarantee if these sites are valid or not)  http://www.bing.com/search?setmkt=en-US&q=MANUAL+FOR+OPTICOM+B300 

1. Lift up the handset.

2. Press the STO button (for 'Store')

3. Key in the full number you want to store, e.g. 01234 5678910

4. Press STO again

5. Press one of the numbers on the key pad that you want to be the Quickdial number, from 1 to 0

6. Press the MEM (Memory) button.

7. Replace the handset in its cradle.

8. The Quickdial number will now be stored and you can call it by lifting the handset (or pressing the speakerphone button) and then pressing the MEM button followed by the single number you chose.

Source > http://www.fixya.com/support/t11245754-opticom_b300_corded_phone_manual