You firstly ought to get yours valued. Be careful, go to atleast 3 agents and usually it's best to take the middle valuation. Then listen to their terms carefully. Some tie you in and charge a fee to leave them. Then once it's on the market you hopefully will start getting viewings and offers. If you accept an offer you then can instruct a solicitor to over see the sale. In that time you will be looking to buy and the solicitor, once you have an offer excepted will over see that too. Your current mortgage will be paid from the sale and a new one set up. If you like pm me. Happy to help.