The first thing you have to do is press the X button to access the main menu> access Stock> then Tool Bag to find your tools.
Click on the one you want and bring it to the two bars marked 1 and 2 and place the tools in a square. It is feasible to place all the tools on one of the bars and use it as a dedicated toolbar, leaving the other for seeds and other similar items.
That's all you need to know about equipping tools in Story of Seasons Pioneers of Olive Town, we hope you can get the most out of your toolbar.