Hi Littleprince,
Capital gain should be filled out in *schedule 3.
T3 and T5 are slips mailed to you, you don't fill in any of those.
After you filled in the capital gain amount on schedule 3, you only have to report half of the gained amount on line 127 (p.2 of your T1 return)
You cannot claim capital losses on 127 unless you pass away in the tax year... read the info guide for more details
*If it's stocks, put in amount 131 and 132 on schedule 3
*If it's gains from T3/T5 slips, put the amount in either 176/174 on schedule 3