My router/modem is located in the garage because that is where our Gigapower box is located but my office is all the way on the opposite side of the house and upstairs. Using WiFi is tedious because everyone in my house (two roommates and a child) also use WiFi for work/school. Should I be looking for any plugs in the wall or something that I can possibly connect an Ethernet cable to? I have a socket in the wall that says CAT5e+ but I’m pretty sure that is for house phones. TIA.
Edit: My answer is targeted to the very little information posted at the time. The question is could this work, not what's the best way or fastest way.
Cat 5 cable and RJ-45 jacks have eight wires.
100 Mbps Ethernet uses two pairs (four wires), one for send and one for receive. Telephones use two wires.
Therefore, you can run both ethernet and telephone over the same wire, and still have two wires left over. It all depends on how your home was wired. The outlets may need to be reconfigured, but it's easy to test if you can find the junction box and see if you can plug in an ethernet cable from the modem. If it works, problem solved.
The caveat is that the maximum speed under ideal conditions is 100Mbps. The actual speed might be lower.
An alternative solution, rather than wiring up your whole house with ethernet, would be to buy a few WiFi Repeaters and set them out where ever you need a stronger signal.
You can go fairly basic (e.g. NETGEAR Wifi Range Extender) or as fancy as you want (e.g. Whole Home Mesh WiFi System). Even at the fancier end it'll probably be a cheaper solution than hiring an electrician to run all that CAT6. Of course if you really want to run your own ethernet cables, who am I to stop you.
CAT5e+ sounds like an ethernet connection. You can try to plug in an ethernet cable and see if it fits; phone sockets can't fit ethernet cables.
Try to find the other end. Look in the garage, utility room, attic, or basement for a cluster of sockets/wires. (Although it could be anywhere.) If you're lucky, the actual sockets/wires will either be numbered or labeled such that you can tell which socket goes to which.
The standard setup is to have one cable from the modem in the garage, going to the cluster, where there will be a switch, and wires from there to all the rooms that need internet.
In the event this is actually a phone wire, that's probably not the end of the world. You can use it to pull real ethernet wire. Just securely attach the ethernet wire to the end of the phone wire, then pull from the other end.
Alternately, I think Powerline Ethernet Adapters are actually okay, or at least better than wifi.