If your partner is submissive it means they are willing to give themself to you completely and let you be in control. You are the dominant figure during your session and lead them where you want them to go.
When you are going to try your hand at being dominant you need to discuss some boundaries with your sub. One of the most important things to do is establish a safe word so that, if it gets a little too intense for your submissive partner, there is something they can say to let you know. It is best to make sure they are comfortable and happy with how things are proceeding throughout the session, so arrange some way for you to check that everything is okay. If there are certain things you wish to try beforehand make sure it is within their capabilities and boundaries and, if they are not comfortable with it, don't force the issue. Submission does not necessarily mean being a slave (though it can be a part of it for some) - it means being able to give yourself over to someone and, most importantly, being able to fully trust someone will take you to your limit and no further.
There are a wide variety of different tools and toys to try with your submissive partner, and all can help to enhance your experience as dom and sub. Some submissives wear collars (either around their necks or more discretely on their wrists or ankles) to show that they have a dominant in their life. Restraints, such as handcuffs, can be very useful for keeping them under your control, and whips and paddles can be fun for a bit of spanking if they stray from their role or your orders too much.
The main part of submission is not the toys, but the mind. For some people, they will want to follow your every command and please you however they can without the need for whips or chains to keep them in line. On the other hand, some may want them desperately to know when they are going wrong, so make sure you discuss this with your partner before you get underway. Over time you will get to know each other better and can learn your limits, which makes these sessions easier.