Ah, no worries. Open Wireshark and select File -> Open. Select the file that was just downloaded from your Fritzbox. You should see the captured packets now. On top, you have a "search bar" that says "Apply a display filter...". Select this and input: "udp.port == 3659" without the quotation marks. This will filter out any UDP packets that are on port 3659, inbound or outbound. Battlefield games since BF3 use port 3659. Now, on top select "Statistics -> I/O Graphs". This opens another window and gives you a nice diagram of all your network traffic. Below the graph you have the filter. First, delete all the preset ones by selecting them and clicking the "-" icon. Next, create a new filter by clicking on the "+" icon. Check "Enabled", "Graph name" set "Inbound to router", "Display filter" you input "udp.dstport == 3659". The column "Y-Axis" governs what's shown. "Packets" displays the amount of packets per interval, "bits" or "bytes" displays the size of the datagrams. You can also do this for outbound traffic towards the game server by adding another filter, checking "Enabled", "Graph name" = "Outbound to server", "Display filter" = "udp.srcport == 3659". Give this graph a different color to differentiate it from the inbound one.
You may then select "Save As..." to create a nice screenshot as I did in the other post.