HOw to Give own dimension?

HI GUys, as my drawing is  not to  scale I would like to  give  my own dimension to the  drawing, but to no avail. I tried to  do the following : Tool > Modify> (  but i can't change the  default  dimension ) I  ahve also  tried command  MP (  but  again  I couldn't change the default dimension )  Can someone lead my hand and show me how? TIA.. I  seldom come to this forum  hence  will appreciate if  someone can email me  the  solution  to  rt@live.com.sg..

Manual input while drawing the dimension in the tool options bar above the drawing area, or afterwards via Tools - Modify - Properties.

Thanks for the reply. My steps is as follows: TOOLS, DIMENSION, LINEAR,
It prompt me to specify  first extension then  prompt  specify second extension then  it came up with the default  Dimension in the drawing and ask to specify dimension line location, I tried to type a different  dimension it yield Unknown command!! I'm using  version 2.1.3.

Is there  some steps I'm  doing  wrong?

Would be  glad to  solve this!

Thanks and cheers!!

Manual input while drawing the dimension in the tool options bar above the drawing area:




or afterwards via Tools - Modify - Properties:



The tools options bar changes it's content according to the active command. During dimensioning it pops up as shown. You can type in your wanted value before finishing the dimensioning command.

Alternatively you can manipulate an existing dimension via Properties, then selecting the dimension.

Got it!  Thank you for your  assistance!!