Trade query

How do I set up a trade with multiple items (does not include horses)
Please tell me step by step as I am a bit of a techy simpleton 

Go to Marketplace, select create trade. In the box on the right is all the items currently in your inventory. To select multiples that are in a row, press and hold shift button before clicking the top most item and the bottom most item, if the items you want to choose are scattered about your inventory, press and hold control button before clicking on each item.

Must be a technophobe as highlighted 1st set of items but clicking again did nothing but unhighlighted the items.  Have since sent the individual items to the relevant member.  Thanks for trying to help.