You can use the related items field, for the purpose of linking to items.

This field is very powerful for selecting items, but it produces a rather simple list of FLEXIcontent item links.

If you want a more than just a list of items, you could use the universal flexicontent module:

1. Create a new Universal FLEXIcontent module (mod_flexicontent)
2. Configure the module to use the ITEMS scope and set non-static behavior: to display items of a related items field of the current item.
3. Configure the module to use the module template you wish and to display the items with the fields you need
4. Create a new field of type load module and load inside it the module you have created
5. Assign field to the item types you wish and and add it to the templates your item type or your categories use

You are done ! You have a feature rich display of related items