You place a arcane symbol specific to you on a creature (creatures can be anything however this will depend on what your DM allows you to mark) you can touch. The creature must make an Intelligence saving or have the symbol placed on them and be considered Charmed. This symbol once placed lasts forever or untill dispelled. If they succeed the save then the spell has no effect and they arent marked. You can have only have 1 symbol active at a time. If you already reached your limit on symbols and place another one, then the oldest symbol you made will be dispelled.

This creature acts as a familiar and acts independently of you, but it always obeys your commands. In combat, it rolls its own initiative and acts on its own turn. A familiar can attack and can cast spells up to 3rd level that you have prepared, an amount equal to your proficiency modifier per day, and cast cast any cantrip you have prepared. If the spells the familiar casts require an attack or save then use your own. 

While your familiar is within is on the same plane of existence as you, you can communicate with it telepathically. As a bonus action, you can assume control over your familiar, while like this you can see through your familiar's eyes and hear what it hears, attack and cast its spells until the start of your next turn, gaining the benefits of any special senses that the familiar has. During this time, you are deaf and blind with regard to your own senses. Additionally you can spend an action to expend a 1st level and be teleported to your familiar. 

Finally, when you are in control of your familiar you can cast a spell with a range of touch, through your familiar as if it had the spell.