Once you get weapons or armor in Biomutant, that is not the end of it. You can upgrade them to improve their stats via workbenches, but to use a workbench you will first need to find it. That said, you can find these workbenches usually at both towns and outposts.
There will be floating yellow balloons floating above at these locations, and you will need to climb up them. This is because there will be two workbenches you can use at the top. One will be for weapons, and the other will be for armor. To use the workbench, simply walk and up use the interaction key on one of them. After this, you will be able to upgrade either your weapons or armor, depending on which workbench you use.
Related: How to get a Mount in Biomutant
Upgrading will also cost resources so depending on what you want to upgrade, so you will need to gather the items beforehand. Luckily you find most resources by exploring and fighting enemies. However, we highly recommend waiting until you get some really decent or high-level gear as upgrading will cost a lot. So for the time being you will want to just create new weapons or armor, as it will cost less in the long run.
That being said, when you upgrade an item, you will raise its level along with its damage output, and it's various stats. Because of this, it's definitely something you should keep in mind when gather materials, but only when you are ready.