Given that you started out in December 2013, you should have registered as self-employed with HMRC so that you were issued with a tax return year ended 5 April 2014. You should either call the tax office on the number here
to register now or read the notes here
and register online. You may have to pay some interest on tax paid late and penalties registration. These can be appealed.
The personal allowances /14 and 2014/15 are age dependent and you can find them here
. You won't pay Class 4 National Insurance Contributions as you are over state pension age, though that may not have been the case in the 2013/14 tax year, and your self-employed income was below the start point 4 NIC.
If you work in the same place, you cannot travel costs I'm afraid, though you may be able to make a claim if you work at more than one site. Any other expenses you wish to claim need to be put into the self-employment pages. You should draw your accounts up to 5 April 2014 and then to each 5 April thereafter to keep things simple and only show self-employed income and expenses from December 2013 to 5 April 2014. Any tax you have to pay will be at 20% if the sum of your state pension and self-employed income is more than your personal allowance.
I hope this helps but let me know if you have any further questions.