Thank you so much!
If you're stuck RIGHT at the beginning you need to go North from the town into the science lab, there you can get the omni-tool and begin harvesting materials.
If you're stuck on the fishing quest, there are a few options to get past that. I'll give you one method and leave you to figure out the others if you want the extra challenge. The most direct solution is through tool mods. Beck's Tech sells a mod called Squanto 1, once you install that in your Harvest tool you will sometimes find random fish while chopping down trees or mining stones. Beck rotates his stock of mods daily, so you may have to check back multiple times before it shows up in his store.