=A1+B1 will do it.
What you may need to do is change the Cell Format for the cells to:
[h]:mm
You can do this by selecting the cell and going to:
Format | Cells | Number
Change to Custom and type [h]:mm in the line provided.

For details about working with time, see Chip Pearson's page:
http://www.cpearson.com/excel/datetime.htm#AddingTimes

tj

"Tricia" wrote:

Hi what format do I need for the cells in excel for adding time as in 01:35
(one hour thirty five minutes) + 12:35 = 14:10.

Or where can I find a tutorial or example.

Thanks Tricia